If this person can unlock your phone and open your Coinomi app, he can just open the App and view the seed. This can be done at anytime using coinomi.
This is why I don't store any crypto on my phone anymore, and I used to use Coinomi and Electrum for Android. I tend to be a bit careless as far as keeping my phone secure, and if I had lost my phone when I had those wallets someone could certainly have taken all the funds off of them (not that I ever kept a huge amount on my phone). I figured that it's just too damn easy to lose your phone that I didn't want to take a chance and quit using mobile wallets altogether.
but is one of the best close source wallet
Coinomi would be such a fantastic wallet if only its code were open-source. I've never had any problems with them, but I can't say it doesn't make me just a little bit nervous knowing that the code hasn't been reviewed by any independent parties. I guess I could say the same thing about Ledger, too.