I can see most but not all using the “name photos “ workaround. I can see the top conversations in storage>messages and that shows the approx correct amount storage. I don’t think the photos are gone, gone but there is definitely an indexing bug in the iMessage photo gallery that isn’t allowing photos to populate in there. If I scroll back in a text thread the photos are there. I didn’t have this problem in iOS 18. It started iOS 26 at least for me.
Searching online, this seems to be a widespread issue so I’m surprised Apple hasn’t bothered to fix it yet. I use the photo tab/ gallery a lot so being without it is annoying