"I've tried laying my phone over the receipt, but it just doesn't work."

Nevertheless, this is the answer, and much better than the proposed colored card.

Some large chains have a miniature payment kiosk at each table. You just pay when you’re done and leave. Very convenient.

I seem to be alone but I like the places where I order and pay on my phone and then they deliver to the table. For me it is the best experience.