The United States Supreme Court's announcement Monday that it will no longer hear arguments in transgender student Gavin Grimm's bathroom lawsuit left LGBTQ advocates disappointed and scrambling to regroup.

"It’s not just about bathrooms, it’s about the right of trans people to exist in public spaces," Grimm, a 17-year-old Virginia high school student, said on Monday after the announcement. "If you had to plan your day around not having a bathroom in public, what kind of nightmare would your day be?"

Grimm, who identifies as male but was was assigned female at birth, sued his Gloucester County, Virginia, high school for denying him access to the boys' restroom. The case climbed its way to a scheduled March 28 Supreme Court hearing, but a Trump administration move to alter the government's guidance on the issue caused the justices to remove the hearing from its calendar.

Related: Supreme Court Rejects Gavin Grimm’s Transgender Bathroom Rights Case

Grimm was in class this morning when the court announced it was declining to hear the case. His phone buzzed with Facebook and text messages from friends, he said. While "disappointing," the news did not shock the high school senior.

"The Supreme Court has missed an opportunity to end the painful discrimination currently faced by tens of thousands of transgender students nationwide."

"I was aware that it was a possibility, so I tried to keep myself open without any expectations," Grimm told NBC News. "I was as prepared as I could be for that possibility. I’m in for the long haul. If it takes 10 more years, I’m happy to be a part of it."

Now, the case goes back to the 4th U.S. Circuit Court of Appeals to be heard all over again. There, lawyers for both sides will have to argue two main questions: how much weight should be placed on the federal administration's interpretation of Title IX, the federal law protecting civil rights in education, and does Title IX include gender identity in its definition of "sex?"

The Morning Rundown Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

In the meantime, sending the case back to a lower court extends a period of confusion over what Title IX does and does not do — confusion expressed by White House Press Secretary Sean Spicer when he said during a February 23 briefing that "the law that was passed in 1972 did not contemplate or consider this issue."

Advocates remain convinced that Title IX does cover transgender students, but they are aware that some parents and school administrators are unsure of the law's scope.

"The Supreme Court has missed an opportunity to end the painful discrimination currently faced by tens of thousands of transgender students nationwide," said Eliza Byard, executive director of GLSEN, a group that advocates for LGBTQ youth in schools.

"There does need to be a clear statement of what the law is," said Lambda Legal attorney Demoya Gordon, who works with the firm's Transgender Rights Project. "The recent action by this administration to rescind the guidance really just injected confusion into the area, whereas there had been some clarity provided before."

Gordon cited a handful of cases that similarly aim to define Title IX or the Constitution's Equal Protection clause, or both. One recent success for the law firm came on February 27, when a Pennsylvania district court judge ruled in favor of three transgender high school students who had been refused access to restrooms — one of whom is the sister of Jackie Evancho, the young singer who performed at President Trump's inauguration.

Other cases in Ohio, Wisconsin and North Carolina have recently ruled on the same issues. Just like the Grimm case, some of those rulings referred heavily to the Obama-era guidance to schools, throwing the rulings into question after the Trump administration withdrew it.

By the time Grimm's case is settled, he will have graduated high school and turned 18. In a phone call with reporters Monday, he explained that his senior year has been full of the usual stressors like getting ready for college and balancing credit requirements. But Grimm experiences additional stress that his classmates don't necessarily have to deal with. He says that he avoids using the restroom for as long as possible, and "in situations where I cannot avoid it I’ve been in the nurse’s room."

"When you’re singled out and sent a direct message to you and your peers that there’s something about you that needs to be segregated from the rest of the student body," Grimm said, "It can add an extra level of stress and duress."

School policies regarding transgender students vary by school, by district and by state. Some trans kids get to use the facilities that correspond to their gender identity, while others are made to use facilities that correspond to their sex at birth. The latter policy is especially confusing for intersex students, who are born with male and female traits like chromosomes and sex organs.

Many hoped a Supreme Court ruling would create a uniform policy for schools across the nation. But that will have to wait.

"While this plays out in our courts, we are deeply concerned about the consequences this could have for transgender students, who may not be aware of their rights or be subject to increased discrimination by others who feel emboldened by the Trump Administration’s recent actions," Human Rights Campaign (HRC) Legal Director Sarah Warbelow said.

Another HRC employee, openly transgender press secretary Sarah McBride, said in a video message posted to Twitter that the fight will continue.

To all the transgender young people wondering what the development in the Grimm case means: this delay is not defeat. The fight goes on. pic.twitter.com/nh6wd8rVjV — Sarah McBride (@SarahEMcBride) March 6, 2017

LGBTQ advocates noted that the Gavin Grimm case had become the most high-profile example of the battle over sex-segregated bathrooms, but its potential civil rights impact extends far beyond just the question of who should pee where.

"This has never been only about the needed clarity this case would have provided, but the message that all of our institutions — schools, courts and government — should be sending to trans youth everywhere," PFLAG's interim director Elizabeth Kohm said. "That they are loved, that they are valued, and that they will be protected in order to access the same educational opportunities afforded to all youth in our country."

The Grimm case, for many Americans, has become an introduction to the daily lives of transgender youth. Writer Hannah Simpson, who is transgender, expressed her concerns about the impact delaying the case could have on trans kids who already face discrimination and would benefit from a final ruling on their civil rights.

"When we send a message that this can be settled on a case-by-case basis, we’re saying this can be decided case-by-case in every living room," Simpson said. "It's promoting the fantasy that a parent has some inherent domain in the gender of their child. This is not something you can decide like a curfew or piano lessons."

Simpson said that all transgender Americans stand to be affected by the ultimate decision in the Grimm case, not just kids. When Simpson was a medical student, she said she was asked what she "planned to do about bathrooms." In response, she joked, "I plan to continue using them."

Follow NBC Out on Twitter, Facebook and Instagram