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1) No, you did not possibly start a fire. However, the Ortho bug spray is a liquid and as you know, liquid and electricity do not mix well together.
2) Since the receptacle was a GFCI type, this was a good thing as the GFCI would have protected you from a shock if there was a ground fault and you came in contact with any live wires.
3) In the event that you need to spray this receptacle or any others within the house, I would recommend to turn the circuit breaker to the OFF position and then temporarily back out the receptacle or wall switch from the wall. Leave the wires connected to the devices and perhaps place a small sandwich bag over the devices and wire nuts to protect them from getting wet with the bug spray. Then try to wipe the interior of the wall box, perhaps reverse your shop vacuum cleaner to blow air into the box in order to make the wall box is completely dried out. Leave the devices hanging out of the box for a few hours to make sure all is dry. Then re-install the devices into the box and turn the circuit breaker back to the ON position. Reset any GFCI's and you should be good to go.
You may want to perform a visual inspection of the interior of the wall box and the GFCI receptacle to make sure it is completely dry. If not, refer to my suggestion that I mentioned above.
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