what will now happen with that transaction. Is my btc lost in transit forever?
I will bold the answer, since it may be lost in the "sea" of ideas how to make your transaction go through.
also your Bitcoins are not lost forever if the fee is too low miners may not confirm the transaction except maybe you use a free accelerator. But if the transaction is left unconfirmed for a maximum of about 2 weeks the Bitcoins will return back to your wallet
So the transaction will either be confirmed, either will be dropped and in the second case the coins and the fee will return to sender wallet, like nothing has happened.
Just I will add something to this: the 2 weeks is not a precise or even reliable deadline. If the fee is low, some nodes will drop it faster. Certain nodes, some so-called "free accelerators" and even some wallets will keep re-broadcasting the transaction and then even after 2 weeks it may not be dropped.
However, historically the fees had high and lows, so re-broadcasting forever never happened. And of course, the sender can act (rbf either for up the fee, either for canceling, or cpfp for the change), the receiver can act (cpfp), so you still have a certain amount of control there.
PS. OP, you've posted while I was writing this. If it's not useful please PM me and I'll remove.