Do you think its possible that a member of the Ent-E crew stayed behind in 2063? Or were left behind by accident? Or all crewmembers were accounted for?
I'd guess they'd be meticulous about scouring Grevitt Island and the silo site in Montana for anything that could contaminate the timeline. You know, beyond all the contamination of hanging out with Lily Solan on the Enterprise, launching Riker and Geordi into space on a historic warp flight, and sending hoards of Starfleet Engineers down to the launch site might have caused.
They apparently also were content to leave that Borg debris and those drones remains that weren't beyond resuscitation at the Arctic to be discovered a century later in Enterprise. Though of course that wasn't the fault of the FC movie.
This sounds like something that should be covered in one of those Trek short story collections from Pocket Books. Kor