If you sent the BTC to your nano, it's likely that somebody replayed the transaction onto the BCH network, unless your ledger was using a segeit address.
That's actually impossible... BCH has full 2-way replay protection... BTC transactions are not valid on BCH network... BCH transactions are not valid on BTC network.To get your BCH: Download Electron Cash (a Electrum fork for Bitcoin Cash), import your old Electrum wallet and send your BCH to your Nano S Bitcoin Gold address.
errrr... I really hope you meant Bitcoin CASH address!! haha... Man, so many "Bitcoins"... gold, cash and now diamond... getting confusing! 
In any case, I'm pretty sure that you CAN'T accidentally send to a BTG address... they changed the address format, so it SHOULD get rejected.