Nothing really concrete, but can you not take a screenshot of the address if it's still logged there on coins.ph? That may satisfy some but not others but someone will likely buy your account without a signed message but it'll fetch less and I wouldn't recommend it.
I see , but the address wasn't logged in there anymore, it was replaced with a new one
This is why you shouldn't just use exchanges. I'd suggest associating an address with your account asap. Someone then may accept it as proof in the future though it wouldn't prove your account wasn't hacked before then.