Mixfinder -
I don't think one of our little furry friends could have gotten in there. The gaps between the outer and inner tubs in a belt-drive WP product are very small. He would need to have X-men characteristics to get in there. Good idea though - if this were a filter-flo, that would be very possible.
Much more likely I think is that the pump is simply worn (or maybe even deteriorated from the guck that was in there). It won't pump if it has to send water to a stand-pipe height locale, but it will if it goes downhill, almost as if in a siphon. This is the sign of a worn or broken pump. Because water will flow out, it eliminates a clogged lint filter or hose, etc.
I have not personally seen a pump do this in a while - maybe once in my 'career' rebuilding in the 90s, but one of Kevin's did the exact same thing last year right in front of me, and we decided it was the pump. Later when he installed a replacement, it solved the problem.
I'll post it here when I find out!
Gordon