get [transitive] to go to a place and bring somebody/something back SYNONYM fetch
get somebody/something Quick—go and get a cloth!
Somebody get a doctor!
She went to get help.
I have to go and get my mother from the airport (= collect her).
get something for somebody Get a drink for John.
get somebody/yourself something Get John a drink.
You found out that your child "threw your T-shirt under the bed" (not sure if it is ok to say like that), would you say "go get it under the bed for me, please"?
The part "get it under the bed" sounds a bit awkward