If you got the gold 1 chest then you are at bottom of gold1 after reset. One loss will push you down to silver4.  This is likely what happened.  If you had been dropped to bottom of silver4 the one loss would have dropped you to silver 3.  

It's always been this way.

Please correct me if I'm wrong, but if I make Gold 1 at the Arena reset, shouldn't I start at the bottom of Gold 1?  For the second week in a row I have been pushed all the way back to the bottom of Silver 4 after receiving my reward for the Gold 1 tier.  I thought maybe I might have lost a ton of defense battles which could have pushed me back, but that isn't the case, since I only have 1 battle in my log that occurred after the reset, and it was a victory. Am I misunderstanding the process?