I was was bottom fishing this past weekend and hooked into an enormous nurse shark that really put a bend in my rod. As I put the next bait down I noticed that one of the rings had popped out of one of the eyes. I figured the guide had cracked allowing the ring to pop out. I just pushed the ring back into the guide as a temporary fix. After that I used another rod for the rest of the day.

Problem is I don't really remember which guide it was. I have gone over the rod 3 times now and can not find a loose ring or a a crack of any kind in any of the guides. Any suggestions? Is it possible that some how under stress the ring just popped out and I was able pop it back in place?

Yes, it is possible, but if it happened once it'll happen again the next time the rod undergoes similar stress.

You can run a Q-Tip swab around the inside of the guides rings. If there is a crack it'll usually pull some cotton out of the swab and identify itself.

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Assuming that these are larger guides (base in the type of fishing you are doing).
You can take a tooth pick and some Gorilla shock resistant supper glue, and run a thin line of glue around each of the guide frames against the insert (each side). Which will reinforce all of them and repair the one that is loose.
It will wick into joint of the one loose insert and re-glue it to the frame.

I have done this several times with good success. Even with some of the old style Batson Micro guides before they redesigned them. Have yet to have one the new designed Micro's fail.

I knew it had to be one of three guides so after some pretty strong pressure I was able to push the ring out of the bad guide. I haven't taken the guide off yet and my eyes aren't what they used to be but I think I can see a crack in the guide. I would not have felt comfortable gluing the rings. I'm sure it would have failed again at just the wrong time.

Thanks for all the advice.

Robert,
If the rod has had a lot of use, you might consider replacing all of the guides at the same time - just to freshen the rod.

Be safe