One presumes that you've checked to see that the chain isn't still attached at the other end to somewhere accessible? It obviously would have been attached at both ends to start with, so seems unlikely that it would simultaneuosly detach from both ends.
Tangentially:
I once fitted a new fuel tank sender to a friends VW camper, which entails removing the engine/gearbox, and then the fuel tank.
Once the job was completed he went off on his European tour, but complained that the engine would stop after around 2 hours driving, but after being left for 10 minutes it would start and do another two hours.
Any guesses as to what the cause was?