Coinbase not moving funds in wallets since 2015?

I was looking at my Coinbase account history last night just for kicks and nostalgia. Specifically, why I was sending 1.0 bitcoin to certain accounts in 2015.

There's a transaction that I have that goes from Coinbase, to a Mycelium wallet on my phone, and back to Coinbase, and that's where it "sat", until I eventually moved it to cold storage.

The problem is, that's not the end of the trail for that specific bitty. Looking at Blockchain Explorer, I get this:
16f993ab4124551cd3e7d692b6c3244fd3c3e9c98cb420c44284813a02df80a0
I sent 1.00039465 from my wallet to my Coinbase wallet.

2b5e834ffe4a872e8d122223b6c517bb12e305ca7fc626903f56eebe8df02daf
Minutes later, without record of this transaction on my Coinbase account - I'm assuming this is background activity - it's moved to another wallet.

45903b7b2eac8a902504cde7981b8b4d7e30e4eb5ca4567a3b574389ab12a431
Then moved here 11 minutes later.

f7e559a4472c56a7757ee1f79b3cfec8ddf9db5fbdb72a951f864e45de7c7298
Then moved here (automatically??) where it sits. And has sat since Oct, 2015.

Is this a lost Bitcoin that Coinbase has forgotten about? Is this normal procedure?? What used to be $320, is now $60,000, unspent. I'm just super curious about this (and also helping me learn about the blockchain and exploring).

Any ideas?