A developer who specializes in the Bitcoin digital currency says he was sent back to China last week after he arrived at Sea-Tac Airport with only $600 in cash and wasn’t able to convince U.S. Customs and Border Patrol agents that he would be able to fund his two-month visit using Bitcoin.

The developer, who goes by the alias “Doctor Nefario,” identifies himself as the founder of the Global Bitcoin Stock Exchange. He was coming to the U.S. to work with entrepreneurs Mike Koss and Peter Vessenes at the StartPad offices in downtown Seattle, said Koss, the StartPad director. Koss has been contemplating Bitcoin-related projects, and Vessenes has been working on one.

Koss says “Nefario” even paid StartPad in advance for a desk at the co-working space … in Bitcoin.

“With three of us in the office working on or thinking about Bitcoin projects, we thought we’d have a quorum to have a ‘Bitcoin Development Center’ based out of StartPad,” explains Koss via email. “With Nefario’s turn back at customs, we’ve lost some momentum on that.”

Nefario (whose alias is a reference to a “Despicable Me” character), gave more of his background in this interview with Bitcoin Weekly in June, describing himself as a cypherpunk. He chronicles his recent attempt to come to Seattle in this blog post, saying that the custom agents were courteous but highly skeptical about his explanation of how he would be paying for his travel and accommodations.

I was put into a small office when the five to six hours questioning began,did I have a credit card? How come I ony had $600? What the hell is bitcoin? Although I was cash poor I had more than enough bitcoin to cover all the costs of my trip and stay, I was going to be meeting with bitoption later that morning in Seattle, he had $1500 of cash to exchange. I explained this to the agents and then the topic of the questioning turned to how bitcoin worked. After about an hour of that, they took my iPad and brought back my phone, asked if either of them were locked, and then made copies of what was stored on both. They searched me, and my bags, I was questioned and cross examined on who I would be visiting, what I would be doing, and how I exchange bitcoin for dollars or services , how I got the bitcoins… for hours.

Nefario describes himself in the post as Irish and British and says he was travelling to the U.S. under the Visa Waiver Program. In the end, customs agents informed him he wouldn’t be entering the U.S. and sent him back to China, telling him that he could apply for a Visa to return in the future.

Koss has refunded Nefario’s rent money, transferring the Bitcoin back to him, but the StartPad guys are still hoping to collaborate remotely with him on Bitcoin-related projects.