Sow a few more seeds direct into the ground. The soil is damp, we have warm weather coming, they’ll germinate quickly. Cross your fingers and with any luck they’ll only be a couple of weeks behind the others.
I would say to definitely chuck a couple more seeds in the ground and give up on that one. I did and to speed things along I put a fizzy drinks bottle with the bottom cut off an took the lid off to make a mini greenhouse effect, and the seeds worked so quickly, I was amazed. But it's hot anyway, so won't take long. I had one completely eaten by slugs, so that's why I started again. Thats if you've got any seeds left that is?