As far as the rest of the gun, it's assumed the owner didn't let the reciever and bolt area get completely buried and filled with dirt. Of course it's not going to work then. It's the equivalent of letting your lungs and belly fill up with dirt. Just as it's not all that difficult to avoid that condition in the owner. It's not all that difficult to prevent it happening to the gun.
A mag should be in place to limit dirt from getting into the bolt/reciever inside areas. Just as one can get sand in their pants though, a coating of sand and dust can get in the reciever. The gun can be hand cycled once, or no more than a few times to clear it and it's ready to go. The mechanism is robust enough that it won't end up in a jam, due to dirt, that's not simple to clear. Using it in such a condition for an extended time will wear it out quick, but it will still fire.
If carried by someone of limited strength and endurance, perhaps could such sloppy handling take place?