I'd consider fear, too. I've witnessed (petit mal) seizures scaring two of my dogs (the approach of the seizure) and also internal pain. The fact that he returned to normal gives the thought of seizure more weight.
Both of my seizure dogs were yellows and both had issues with internal overheating...Honey's were exacerbated by external heat/exercise but we got them stopped with a food change (she was eating kibble, though...I think Cookie's diet of raw is not a factor); Brutus' started out as an issue from external temperature and progressed to grand mal reacting to seemingly nothing (also kibble but it wasn't until the seizures turned into grand mal that we realized what we were witnessing. Honey's came back when she was dealing with the pain/fear that went with losing control of her hind legs (despite the food change).
We were told by our holistic vet that seizures are common at night and actually may have been going on when we weren't aware...neither dog slept with us.
If Cookie's activities have been really energetic lately, it could be overheating from that getting things started (IF it's seizure). Honey started having more issues with exercise before we actually witnessed the first seizure (outdoors in snow in a really cold December).
I'd keep a good eye on him especially when it's warm out or if he's being active in any way. I'd be careful about him swimming away from where I was...even if his feet can touch the bottom, he could sink below the surface with a seizure (Honey would lower herself to the ground like her legs were giving way). And see the vet when you get back home. Lots of times a regular vet won't find anything wrong....Honey was diagnosed by a holistic vet.
If I didn't have experience with seizure, I might be more prone to thinking something external just scared him...but even my tendency toward denial doesn't allow me to think that.
Sending all good thoughts for you and Cookie!!!