You answered your own question - "It sat for a few days before I planted it and realized it never got watered in those few days. When I took the tree out of the pot to plant, the roots and soil were really dry."

The problem was lack of water. Making sure the tree is well hydrated now is good but don't overdo the watering and keep it too wet. You are likely going to lose some foliage, which may or may not be replaced this season, but it should recover.

Do you think some Osmecote fertilizer would help it out a little?

No. It needs water and time.

its is extremely stressed ... you are not its grandma ... feeding it wont make it feel better ...

see link below.. about timing.. and watering ...

next time you bring a pot home.. put it in full shade ... to give you a few extra days ...

nothing needs water every day ... water when the plant needs water.. insert finger and find out.. its you soil.. your local weather.. etc.. only you can figure it out ...

if you perfect the watering.. and the plant settles down.. it can releaf ... as long as a leaf if green is can process light into energy ... dont cut them off or anything ...

ken

https://sites.google.com/site/tnarboretum/Home/planting-a-tree-or-shrub