This has happened with Bailey a few times, last time the groomer said she was really matted...she was not, she had one matt under her front leg that I couldn't get out (my son washed her and didn't brush her out) I let them know and she said no big deal...I went to pick Bailey up (it was January) and they had shaved her, her hair is starting to grow back.
The good thing about a bad haircut is that it is not permanent.
In the meantime put sweaters and tee-shirts on your (cold) little guy!