If no true leaves come out within a couple days I would assume they're done. The cot leaves supply nutrients to the plant before the true leaves emerge. I've accidentally torn off a few myself when the seed coats wouldn't come off. No problem as I've got over a dozen of each and I'll cull half of them.

I accidentally pulled off 2/3 of the cotyledons of a seedling. It now has tiny little leaves comming out of the stem. Just give it a few days it might be saved.

Thank you for the responses. It has been almost two weeks, so I tossed them out of the tray last night. However, I just now noticed the stems had bent towards the light since they were on their sides all day. Perhaps I'll put them in the window sill and give them a little longer. I hate to see a good tomato plant die. :)

I would consider them an experiment and not count on them to make it. Just see what happens and report back.

Give them a chance! They want to live. I tend to anthropomorphize my plants a bit. I apologize to the seedlings when I have to pull one of the extra ones out of the seed tray. "I'm sorry, you were just as good as the other one, but I only had room for one. I know you would have made beautiful fruit. You will go back into the cycle of life in the compost pile and your spirit will live on."

yeah wait and see what happens i hit one of mine with a weed eater last yr cut off the top half with no leaves left and it produced good / even replanted the top and got some off it too