If something was wrong you would already know. It would never be advised to repeatedly expose your phone or almost any device to having something or someone sitting on top of it but in general it should be ok. Depends on weight…how long someone sat on it (could over heat), etc. I don’t think sitting on a phone should ever be considered “daily life use” but if it’s something that happens to someone a lot it may require a behavior change…for example getting out of the habit of laying the phone on a car seat (maybe place it in the cup holder or if your car doesn’t have a space under the radio or somewhere else investing in a phone holder that fits in a cup holder or attaches to the vent or uses a suction cup to attach to the windshield for example).
But for this specific occurrence your phone is fine. Otherwise you would have already seen screen damage or the frame bent or something.