I think there is a violation for failing to identify themselves and for lacking the mini-Miranda in this communication.
They don't have to put their company name in the return address. Most of them don't since it could violate 1692f(8 ).
You disputed the debt and their only obligation is to obtain verification and mail it to you, which they did. It doesn't say they have to include a message to you.
The mini-miranda says "this is a communication from a debt collector; this is an attempt to collect a debt." If they didn't send you correspondence or demand payment, why would that be needed?
Sounds like they just sent you something that you requested.