Sure sounds like a blown speaker, audio module (or amplifier), or my old favorite - the switch in the phone jack failed.
The audio setup won't drive a speaker through the phone jack....
I had an HT once that had a bad switch on an antenna jack (little bitty thing that cut the "duckie" off when used to drive an external antenna). Worked OK in whatever mode it was in, but you had to take the back off and diddle the thing to get it back if you changed modes.... I was glad to get rid of that thing

....
(From a DYI standpoint, swapping the speaker would be the easiest, I think, even if the speaker's glued in. It's also very easy to test. Testing the jack might be a little harder, and Lord knows what sort of amplifier is in there.)
Seems like everybody's using audio modules for small radios these days - not too expensive, and they install like IC's. Swapping one's a bear if you don't have the right tools, though. (I don't...)
Good luck with this one, Joe.
Regards,