I'm sorry that happened; that's never happened to me. Sounds like other posters have given good advice.
If I reserved an ebook that my librarians confirmed had become permanently unavailable at that library, I would be annoyed (briefly). Then I'd try to borrow the book another way, not necessarily in this order: borrow the ebook via another library app that has a different book list (e.g.,
Overdrive Media Console vs.
3M Cloud Library), borrow from a different
ebook lending library system, or check out a
DTB version from a nearby library.
I've never used the
Kindle or
NOOK ebook lending systems, but I guess those are possible options, too.