The lilac sapling, which had established roots in the ground during the winter in a shady place and stands about 16 inches tall, has been transplanted to its permanent sunny location.  Even with daily watering, while the plant still stands upright and the leaves remain green, the entire plant is still severely wilted after a week's time.  Any suggestions for reviving this plant; or is it a lost cause?  (I live in Zone 5a.)  Many thanks.

Give some shade.?

Welcome here new member! No, it is not too late to save your Lilac. Just grab a lawn chair and place over the sapling and leave it be until the heat wave or intense sun starts to wane. Yesterday was Summer Solstice and that is the longest day of the year and now the days will start to shorten. You've got this! I started using the lawn chair method for shading a Rosemary transplant just this week. It's been effective for me. Good luck with that Lilac. I love the lilac scent.