The teen who plunged six floors to her death during a Tribeca party wasn’t even trying to retrieve her own cellphone — it was a pal’s, police sources said Tuesday.

Imogen Roche, 15, had been drinking with friends in a loft on Reade Street near West Broadway when a boy at the party said that his phone was locked in another room, sources said.

Roche, a talented Beacon HS student and aspiring actress, offered to scamper along the outside of the building to get to a window of the room to retrieve the boy’s phone, according to police.

But as she crawled out onto a ledge, she slipped and fell at 11 p.m. Sunday, the sources said.

The loft’s residents were away in Pennsylvania when their kid threw the bash, which drew up to 20 young revelers, cops said.

An older cousin of the teen resident had been looking after the place — but then left to go out, according to police.

NYPD Chief of Detectives Dermot Shea said cops are probing whether anyone involved in the incident could be charged with a crime.

“The priority in this incident… was, did we have a crime here?” he said at a press conference, adding police are working with the Manhattan DA. “Once that’s put to bed, there will be other issues looked at.”

Additional reporting by Yoav Gonen and Natalie O’Neill