no. if you have stored your private key anywhere (where it is safe), no one can steel your bitcoin in practice.

theoretically you can write down your private key on a piece of paper. then you can loose your entire py and you can not create a transaction quickly (however your address can still receive bitcoin). but you will not loose any bitcoin if you backup your private key. because: you can (whenever you want in future on any pc/mobile phone with internet access) start to use a bitcoin-wallet-software which allows to import private keys and then you have full access to your fund again.

the fact that a transaction is not confirmed does not affect that either the sender or the receiver of funds of a transaction has access to the funds. (depending on whether the transaction is confirmed or not.)