I know someone that called me some months ago that told me he was walking on a road close to his house two people on a bike attacked him and stole his phone. He has his wallet on the phone but did not backup his seed phrase. He lost some bitcoin. He called me if he can retrieved his coins but he can not retrieve it.
So he didn’t set his mind for the worse scenario, and guess what his phone got bad and now he can’t access it he try repairing it so that he can have access to the seed phrase and some important things . According to the repairer he said the problem was the battery and he got new one but it still couldn’t on the phone , then the repairer discovered that the panel was also among the issue ( according what he told me that the repairer said that once he change the panel is going to lose some important data) don’t know how true the panel stuff is because I have no idea on repairing mobile phone , now we are just hoping for the device to on miraculously so that we can quickly copy the seed phrase.
The phone ROM is with the motherboard which is what you referred to as the panel. If the motherboard is lost, he may lose all the data on the phone, but I do not know if there can be a repairer that can be able to extract the data.
I prefer to use passphrase to extend my seed phrase and I backup the seed phrase on a paper in different locations. You can laminate the seed phrase so it can be resistant to water or encrypt the seed phrase on a stainless steel or titanium steel. I prefer the normal paper because I prefer the seed phrase unnoticeable.
The first scenario happened because of carelessness and ignorance. He saved his seed phrase on a phone without backups. Maybe keeping it in an email would have been safer since he can always have access to it.
To backup seed phrase online is not advisable.