Ask the HR for the receipt number, they should have already had it. Or,if you wrote the check, get a copy of the check from your bank. People say that the number is on the back of check.
Ask your lawyer how to get son in, and then do some research to see if it makes sense or not. If I were you, I will have the grandy take my son to get the H-4. This is because I am afaid of the unpredicable of getting the H-1 visa(not status). I will have somebody send my son in. Even if I am so worried, what can I do? I can not go through the gate with an AP while my son holding an H-4.
I am sure you guys will work out. Please follow up.