Is your phone rooted or not? Rooted devices are less secure as the app storage isolation practically exists only in theory after the rooting, making the device a lot more prone to tampering.
Please select a STRONG password for your Coinomi wallet. A strong password is extremely difficult to brute-force. And assuming that whoever accesses your lost device knows about cryptos and doesn't just reset your device to factory defaults and decided to crack your wallet, you will have 90,472 years in average (which is the time to brute-force a 10-digit mixalpha-numeric-symbol password at 2,6M keys/sec) to restore your wallet on a new device and keep on using it as if nothing happened.
Coinomi is a security-first wallet, it has been around since 2014 and no user wallet has ever been hacked or otherwise compromised, and that is for a reason.