Wow maybe your pocket did something 🤔 I know when I pull mine out of my pocket sometimes it will have taken pictures and pulled up settings and stuff but I had to turn on accidental touch protection for it to stop.
Do you have biometrics security enabled, particularly fingerprint scanning? There is a setting that enables the device to automatically factory delete all data after so many failed login or unlock attempts. Yes it's possible to trigger a failed unlock attempt while the device is in your pocket (done it) depending on the device and placement of the sensor. Also anyone that attempts to login or unlock the device and fails gets closer to the phone doing a factory reset. 10, 9, 8, etc, until either the correct password or pin is used and the count is reset or it reaches zero and the phone erases itself. The setting can be found in Settings>Lock Screen>Secure Lock Settings.
I think to add to this, you can also remotely factory reset a device from a nother computer through find my phone so if someone had access to your Samsung account, this could also be another way.
