At the 7:33 mark I steal a German GrW 34 Mortar. It gets quickly killed by the advancing Germans at 7:42, so I lose the whole squad. However, the entire mortar weapon disappears. There is no leftover weapon to be re-crewed. Unfortunately, it leaves a mortar icon on the top right with "0" men left on the squad and an cloaked status icon. None of the remaining retreated men appear on the tactical map.
At first I thought the weapon was destroyed, but there was no way for small arms fire to damage it that quickly.
Here is the replay:
http://www.coh2.org/replay/16009/mortar-team-bug-kolodny-ferma-summer