Find my iPhone lock/erase

Hello, I lost my phone and without reading online ahead of time, I quickly went on Find my iPhone and erased the device but I probably should have marked it as lost first so it can lock the phone and secure it, since reading further, that the phone will not be erased until it is connected to WiFi. So this bring me to question what if someone who has it has my passcode and can access other personal items? Is there a way to go back and mark it lost to lock it???My two options currently on Find my iPhone is to “Cancel Erase” or “Remove This Device” which I don’t want to do the latter since I’m actually able to still see the location of it, which mean the phone is on. How do I know that the content has been erased???Thank you