You can have one without an erection when your asleep, and you may have had erection during sleep. If this is the first time you had oral, your penis and mind may very well be reacting to it
That's what I was thinking since I have not had an erection in 8 days. I also have not had the incident since. And I have no burning or anything else.
You may have had a nocturnal emission. Where the Penis alone ejaculates in your sleep. Usually you get them as a teenager and they go away as you get more control over but even grown men still have noturnal emissions. You may have had them before and this time noticed it.