I feel your pain. I'm trying to sell a car ('93 Eldorado with only 61,500 miles, if anyone's interested!) on the FB Marketplace. A couple of weeks ago, a guy messaged me and told me he wanted to check it out and he would be paying cash. He agreed to meet me on a Sunday afternoon. I messaged him Saturday night and asked if we were still on, and he sent me a big thumbs-up. On Sunday, I went to get the car, drove it to our meeting spot, and waited. Half an hour passed. I messaged him asking if he was having trouble finding the place. I then watched in real time as he read the message, left the FB Marketplace message group, and blocked me. I'm still livid.