Why did I have a wet dream after aneros use during the day?

I had my first proper session with my massager during the middle of the day yesterday. It was great fun and very enjoyable but no super o. I did feel a tingle/small buildup of what felt like an orgasm/penile orgasm and just kept clenching and releasing and enjoyed it whilst it lasted but it just faded out and it was really just 10% of the feeling of an orgasm. It was fun nonetheless though!

This morning I woke up and felt drained(I usually do after penile orgasm so I avoid them if possible because of brain fog etc). I checked the sheets and it looked like I may well have had a wet dream in the middle of the night but I don’t remember a sexy dream or anything like it at all. It’s crazy to me because I’m 34 and thought I was too old for that lol.

Why did this happen?

Has it happened to you?