Yes its possible to happen without any physical stimulation. I usually don't talk about myself in this topic but did experience this from a dream. Just shows how important the brain is.

There are rare cases where the slightest vibration causes the female to crave sex or self pleasuring right at that minute. I saw this lady on Oprah with her husband and just driving in the car does it and she grew bothered by the inconvenience. This doesn't apply in your case but yes it can happen.