DiskDigger on the phone will "find the phone", but it can't undelete (nothing can) without root access. (Even manually editing the raw disk can't fo it without root access - the directories themselves have to be modified, and no non-rooted app can do that.)
But, as belodion said, if you have to send LG information to get the bootloader unlock code (and you do with LG),
at that point the warranty is void, even if you never use the unlock code. So it's your choice whether to unlock it or not.
If you decide to, I'd suggest Magisk, since it's trivial to uninstall it, update and reinstall it when an update comes out. (Although, since the phone is over 2 years old, it's out of warranty anyway, and there probably won't be any updates past Oreo.)
https://forum.xda-developers.com/lg-...nlock-t3614719 is a full explanation of rooting, installing TWRP and rooting. (And, again, I'd use Magisk - if for nothing else than a) it's currently supported and b) there are a lot of useful modules you can run with it.)