Windows open unexpectedly after parking car…
Your key fob has that capability, and if the appropriate button on it was pressed, then the windows will open remotely. The way that you stowed the key fob in your purse or your pocket is the cause.
My 2005 Accord EX and 2017 EX-L have that capability. If you press the unlock button on the fob and hood it, the windows roll down and the sunroof opens. I love that in the summer at work when I walk out to a hot car. It releases up to 43 degrees of heat in a couple minutes.