Looking at the address you provided in a block explorer(OXT Explorer)
it seems your exchange has been reusing that address quite a bit since December to now and has not really cut down on using it. I do not think they have retired the address and it is definitely still under their control.
Is there an official network that manages bitcoin addresses?
No, each individual generates their own addresses and it is entirely their own decision on how to use them. Most people simply use an address once and then put them aside once they are done with them. The address is still perfectly valid, it is just not good for privacy to reuse addresses. Large institutions on the other hand might find it more convenient to reuse since privacy is not their biggest concern.
Depending on how HUOBI uses their addresses, they could have jumbled up your funds with other peoples' funds if they simply re-assign addresses on an as needed basis. It is generally good practice for exchanges to generate separate addresses for each user to avoid an accounting mess like this but not all exchanges do this.
They definitely still have your funds somewhere in their systems and might just be too lazy about getting it back for you. Go to their website and open up a support ticket or something. Keep pestering them to find your funds or they'll just BS you about "we retired the address" and hope you let them keep the funds.
The beauty is you can track everything on the blockchain, you have proof you sent it to an address they control (they still control) and you can prove the transaction went through. If they make it difficult, you may have to open up a legal case against them with a regulatory body but they definitely have your funds.
It makes no sense for them to toss a seed after just 2 months of use especially since they can generate infinite addresses from just that seed.