Sounds to me like the a/c hold was frozen shut, happened on a GSM 767 in MAN a few weeks back. There is a system to heat the seals when hte a/c has landed, but if this doesnt work and its not a warm day there isnt much the engineers can do.
Hence the baggage's guys leaving the a/c then with no one else to do it, the engineer's may have been asked to help with the offload once they got the hold open...
GJ Engineers
