This is just something you have to deal with when selling. You suck it up and move on but here is how you deal with it beforehand:
You tell the buyer you will be at the meet location at a specific time and that you will be there for 15 minutes. After 15 minutes, you are leaving unless they contact you.
Sometimes bad stuff happens to people like a few years ago I had a CL transaction and the guy didnt show and wouldnt reply. Turns out he was in a bad car wreck and hospitalized. I ended up doing the deal with him but had to go to his house cause he had pins in his legs. Ironically, I was selling him a bike rack which he wouldnt be able to use for 6 months. I think I ended up just giving it to him. I had another guy get pulled over for speeding and then arrested for an unpaid tick. Stuff happens and some people are disrespectful. I have been selling online for a long time - Be clear that there is a 15 minute window and that is it.