I loaned out a Selmer USA bass clarinet some years ago, and never saw it again.
I have borrowed his bass sax on occasion, so I felt comfortable doing so., However, the guy to who(m) it was loaned (and who used to play with my group) apparently loaned it in turn to his somewhat unstable girlfriend.
Fast forward a few months, and I got no response when I asked for it back. I imagine that the unstable girlfriend moved on, taking the horn with her.
(As an aside, all of the female bass clarinet player of my acquaintance (and I have known quite a few over the years) have been both flaky and promiscuous. I guess you have to take the good with the bad...)
Beyond requesting it back a few times (and getting no answer), I've not taken any other action. It was an old horn, bought for my daughter while in junior high (and after which purchase she promptly broke her arm in three places), and I don't really miss it that much. Also, it was one that was never on my inventory (I don't have the serial number) - hard to pursue a stolen property issue without that kind of information.
WIth that single exception, I've never, not once, loaned out a horn without being there as it was being used, and bringing it to the event and taking it home the same evening. And, even in those cases, I am as nervous as hell the whole time that it's not in my personal, direct custody.
Occasionally on Sax On The Web and elsewhere, you will see requests for information on locations that will rent out horns like baritone saxes, bass saxes, bass clarinets and the like. Other than the now defunct Saint Ann School Music Service, I've never known of anywhere that does this. (At various times, I rented English horns, a bass saxophone, and a Eb contra-alto clarinet from them for various Broadway shows that I've done.) And, Saint Ann is out of business long time passing.
Push comes to shove, if you are going to be needing a baritone saxophone for something, you should really own your own, be prepared to schlepp it around to where you need it, and get paid for your troubles. (For example, the AFM contract down here in Houston specifies "spiffs" for those who have to haul big horns like harps, bass clarinets, baritone saxes and so forth.)
School horns are not always available when you need them (and are often beaten to death when they are available). Better safe than sorry.