I believe mine was due to having a panic attack while I was on a family vacation somewhere between 2002 and 2003 (I used to think it was 2002 but we have a video of that vacation and it was before I had the attack).
I got to the hotel but started panicking because I couldn't sleep in the bed there because it wasn't home. I had to go to the bathroom, try to throw up, go outside, walk around, go outside with my mom on the steps to get some fresh air, and all that other goodness. I couldn't feel safe in the room, so I had to go out to the car to spend the rest of the night. I'm not sure I got two hours of sleep. I begged my parents to just let me leave, but they couldn't because of check-out time (or so they say.. I think they didn't understand how bad it felt)
My parents took me home the next day and I got jet-laggish when I got back. I took a nap, woke up, thought it was the next morning and that threw me off inside. Then I lashed out into a panic attack that lasted over a span of a day or two. I had to always be near the door, I couldn't sit down inside unless it was by the door, I had a washcloth on my head at all times, and I darted outside more than once.
I slowly got unable to do more and more basic stuff. At one point I refused to come out of my room, even on Christmas to open gifts. I found it hard to go to school and I had to make special accomodations for myself like standing/sitting at the top of the gymnasium or auditorium during assemblies instead of sitting with the class, or going to the guidance office instead of PE because I was afraid of the gym due to its height. Everybody was getting tired of me doing that, I'm sure
Eventually, I managed to get out of my room, and even get into town and into high school with relatively little difficulty. But, I'm still essentially homebound except for school.