Re: LCD 16X2
What you're looking at is an COB (Chip On Board) package where the silicon die is physically glued to the PCB. Contact wires are run from the die to pads on the PCB, and the whole thing is potted in epoxy to protect the chip.
Identifying those tends to be more of a reverse-engineering project than a document search. Many such chips are made especially for the vendors, or are things where you only get a datasheet if you buy in bulk and sign a nondisclosure agreement.
The usual way to learn how such chips operate is to put them in the original system, connect all the leads to a logic analyzer, and watch the traffic while the system starts up and displays data. Certain processes become familiar after a while, so you learn to spot delays while charge pumps warm up, SPI traffic, etc. Then you dig through the datasheets you do have for devices that might be similar, make some more educated guesses, and write a bunch of test code.
There's no single-and-easy way to get a datasheet though.
When you void a product warranty, you give up your right to sue the manufacturer if something goes wrong and accept full responsibility for whatever happens next. And then you truly own the product.