Turning back for paperwork? Why not just get approval over ACARS to sign it yourself and continue? The jet doesn't know if it's signed off or not. Neither does the weather. Must've been a cadet...
Start making assumptions on bad paperwork is the road to lots of hurt. In reality the discrepancy should have been noted pre-departure, but lots of holes for this to get where it is. There's even the possiblity with non sign offs that maintenance was not completed and things were still in a mess somewhere in the aircraft (not saying it applies to this flight). So yes if you are early into the flight and a maintenance discrepancy that affects the legality of the flight is noted, you turn around. Hmm and since when does a pilot have the authority to sign off engineering actions...
Reminds me of the time two jet captains on 121.5 briefing each other on an ILS because one did not have the charts (pre-Eflight bags) and the destination was down to minima....