That can be true(I often noticed in retail that salvaged 'Mechs would have trouble 'spotting' for the salvage craft to pick up other 'Mechs), but it can also manifest with the Mechs you brought with you. I often wait(ed) until near the end of a mission to salvage anything, to ensure I spend the RPs on most expensive/rare Mechs on the field.
For example, I have a long-ingrained habit from retail to wait on calling a repair truck on the third Carver V mission(the first bandit convoy), as for some reason, calling one in and using it right after taking out the convoy would often enough seem to break my scout's sensors/possibly LOS. I honestly haven't tried to see if it was any different in MCO.
EDIT: I wonder if it's possible to suffer similar damage from head hits on still-living Mechs. I don't recall noticing such a pattern, though.