One could argue that only finding out that it didn't go off actually matters. If an open window provides entry, any action will likely come too late, but is hardly an excuse to not try and return to sender as undesirable. I remember your post, but not verbatim, so I'll have to read about 24 again. Hand grenades won't go off just by dropping it, it will have to be ignited, and when ignition fails, it's about as effective as a brick.

I had an easy time in the Military, as a truck driver I didn't have to sleep in the mud, and the shorter, lighter sub-machine guns we carried were easy on the back. NBC training was a different matter, tear gas filled chambers are no fun, but being familiar with scuba gear did give me an edge.