Never run into this before - this is in IB where they seem to have pretty good short availability. Is everyone and their mom now turning against this thing and shorting it?
I wouldn't use availability at one broker as any guage of anything. The short lending market is famously opaque and idiosyncratic by broker because there is no national broker or NBBO type requirement. Very possible if you'd checked 10 minutes later or at another broker they would have a gazillion shares available, or maybe not. I'd say the short interest (like percentage interest rate) charged is a much better indicator of what you're looking for than if a given broker happens to have inventory.
IB has a tool to show you how many shares are available and from how many lenders as well as rates. There's a small amount of historical data there as well. I'm not sure if they publish who they coordinate share borrowing with (I've not seen such a list). Anyway the tool can be found in the account management -> support -> SLB tool. It is updated every 15 minutes as far as I can tell. Might be worth seeing if there was a trend towards 0 when you tried to short or if it was sort of a gap down and then bounce back up in shares available (ie could have been a bug or something going on with their share borrowing system).
https://www.interactivebrokers.com/en/?f=/en/trading/ViewShortableStocks.php?cntry=usa&a 100,00 shares available at IB right now. A few months ago was the only time my broker offered to lend mine out, very low rate. I will consider at 10-20% but nothing being offered now. I got 20% years ago for ZOES