The grubs are the larval stage of Japanese beetles and/or June bugs. They remain underground until they emerge from the ground in the spring. So yes, they are still in the ground for a few more days to weeks. These grubs are your skunk problem but not your grass problem.

Your problem this summer will the be the grubs produced by this year's crop of beetles. Spraying the current grubs will do nothing against this summer's grubs...although it might chase the skunks away for now, which is what you really want.

You can check for grubs in your lawn in June. Dig up 1 square foot of lawn and count the grubs. If you have more than 12, then you have a problem and should treat for them. If you have fewer than 12, you probably won't notice any grub damage.