Re: Claiming BCH from BTC stored in Electrum and moving everything to Ledger Nano S
[...] and it's not possible for the BTC sent to "vanish", never reaching the receiving address? 
This, for sure, is not possible.
If your transaction is marked as RBF, you can always just create a new transaction spending the same funds again.
This way, your transaction won't be "in limbo".
It might not get confirmed for quite some time, but eventually it will. And with RBF, you are always free to create a new transaction (e.g. with a higher fee).