I had the same issue. Here's a thread that includes a parts list from Amazon for the solution I used.
https://www.montanaowners.com/forums...ad.php?t=88258
This solution worked great, but eventually I ended up completely rebuilding the bed frame. I don't know if the original detachment caused the problem, but I had to rebuild/replace everything under the main stringers that attach to the slide - it all fell apart! I didn't document that process, but if you end up needing to do that, reach out and I'll see if I can find some pictures.
Good Luck!