Did you dig down and see if the corn is still there. Seven weeks is way too long. Danger of frost is just one thing to watch for when planting warm weather vegetables. You have to take into consideration the temperature of the soil. If the soil is too cold the seed will just sit there. Get too much rain and it will rot. You can't sow corn too shallowly or the roots won't be deep enough to support the plant. They should be planted 1 1/2 inches deep. The mulch has nothing to do with it.

I think you should replant. Look for a variety that is early to mature. Different varieties of corn will mature at different times anywhere from 67 days to 80 days

I tried to see if I could find anything by digging and didn't find anything. I guess maybe a squirrel found them, I guess the Albuquerque wind disguised the usual signs of digging. I guess I'm going to try to see how corn does when not direct-seeded.

I use old window screens to cover my raised beds when I direct saw. They are still mounted on light frames so they just span across the raised bed frame. They still let the light and water through but no animal or bird gets the seeds.

You dont say where you are, My corn germinated in a week. Dont plant too deep.

Mine came up within 5 days of planting them.