dualresponse

Good for you!
Bonking is part of the game. A lot of the strongest riders I know will have an occasional bad day and bonk.
"Dude, I totally bonked at 80 miles in" etc..
I know one rider who will consistently bonk the first four or five rides of the year, and then ride VERY strong for the rest of the season.

Think of it as a learning experience. Pay attention to carbo loading, using "goo" type gels before/during ride. Don't try to pull. Hang in, conserve energy.
This sounds like it was a "drop" type ride, which is good, because, they weren't inconvenienced by you dropping off the back. If they rode off- great! It means you can go back out next week, join the same group and try and hang on again. If you get dropped, so what? No one had to wait for you, right? Who cares? Try again!

What you will probably learn, is that this ride has several areas where people go easy, and several areas where they hammer it into a sufferfest- so what you also might be experiencing is potentially a lack of fueling, a lack of personal training, and an unfortunate area on the ride where they turn up the volume to hurt each other, not necessarily you.

If you consistently get dropped, consider a b group, or doing solo training during the rest of the week, focussing on strength, anearobic threshold training, endurance, etc... Before you know it, you will be able to hang. Focus on personal training, riding smoothly and predictably in the group (not hitting brakes, swerving, surging, etc. in a paceline) , put in your sweat equity, and within a year or two, you can be a force on that ride.

edit- rereading your post, I've had a bunch of rides like that, where, I go out too hard, trying to be conservative, not even getting warmed up, or having gone that far, and it's like my body immediately shuts down (more likely, it never started up). It's like a failure to launch, and feels at 10 miles in, just like a bonk at 90 miles into a 100 mile ride. It always seemed to be too much, too soon, and the cards just weren't aligned for that ride. Often, there is also a mental headgame of defeat (at least for me) involved, before the first pedal stroke. It sucks, but the next ride always seems to be better. It's like a bad day at work, you get up and do it again.

Good luck!