Well that sounds like a very scary and painful experience! Here is the good news . . . nothing is showing up now. What exactly that was is a bit of a mystery but an aneurysm does not appear to be the cause. The pain you had all of a sudden and that intensity sure are symptoms of an aneurysm. But the diagnostic tests don't show it. Unlikely they'd miss that. https://www.mayoclinic.org/diseases-conditions/brain-aneurysm/diagnosis-treatment/drc-20361595
Have you asked your doctor about something called a thunder clap headache. https://www.mayoclinic.org/diseases-conditions/thunderclap-headaches/symptoms-causes/syc-20378361
But here are also exercise headaches. Did this occur after one of your bike rides?
https://www.mayoclinic.org/diseases-conditions/exercise-headaches/symptoms-causes/syc-20372276
Lastly, there is something called an Ice Pick headache. It also is very painful and I've suffered this type myself. https://www.medicalnewstoday.com/articles/317234
Are you saying this happened years ago and not since? I'm confused I guess why you're so worried now if the problem went away. The time to worry would be if it came back again, but apparently it hasn't. There are a lot of things in life that can make us hurt that aren't going to show up on a diagnostic test. When you twist your neck violently all kinds of things can happen, including what happened to you. Too much exercise on a hot day without sufficient electrolytes or water can cause a lot of pain. It also could have been a migraine, as you had them after that. My first one happened when I was 13 on a day I didn't eat in the morning, it was really hot, and I went to play basketball. I continued after that to get them periodically for several years. But MRIs don't show that kind of thing. If after 4 years it's never happened again, there's really no way to get a diagnosis. And if it was an aneurysm, I'm guessing there would have been other problems, such as cognitive problems and a difficult recovery period. I'm guessing whatever it was it wasn't that, and given you felt pain in your neck, it most likely came from there. But I don't think you're going to be able to find out unless it happens again and you see a specialist at that time. I'd forget about it and go on with my life, and know that MRIs can't see what isn't there and often not what is, either. Peace.