What is this part?

A mechanic left Mercedes Benz part # A 642 016 2524 off my Sprinter engine. I found it loose in the engine compartment today, about 10 days after having a glow plug replaced. Does anyone know what it is? I would put it back on the engine if I knew where to start my disassembly...... I would guess that it is some kind of heat shielding of vinyl foam. The other number on the item is 01 12233C

Best to all,
Rob

Is it 18 or 20 inches long? Might be the insulation from under one of cylinder covers. If so, it isn't very that easy to replace. By the time you get to where you can put that insulation back under the cover you have done 90% of the work for replacing a glow plug. One school of thought is that neither the covers nor the insulation are really necessary. Maybe save it for the next time a glow plug on that side goes out. You can find some relevant discussion starting with post #22 in this thread:
https://sprinter-source.com/forum/showthread.php?t=47767&highlight=cylinder+cover&page=3