Phone LCD Failure vs Physical or Liquid Damage
The company I work for has a fantastic warranty policy when it comes to replacement phone screens. I know this because I helped create it. My boss and I have spent hours discussing and fine-tuning our policies, but if I put the entire phone screen warranty in a nutshell it says basically that if we replaced the screen on your phone, we will 100% cover replacement for any part failure within 30 days from when you picked up your device.
There are only two exceptions, and that is when it comes to any type of PHYSICAL or LIQUID damage to the replacement part. All kinds of physical damage or liquid damage are not covered by warranty. Not at all. Not ever. No exceptions. Period. We also verbally tell this fact to every customer when they pick up their phone.
Yet there’s room for confusion. We'll get to water damage last, but the biggest confusion happens when some manages to crack the LCD underneath the glass without actually getting any cracks in the glass on top. A trained person can tell the difference just by looking, but as an end-user, you can’t be expected to know if that screen is broken or has failed just by looking at it, so hopefully this will clear things up.
If you can tell the difference then congratulations, you're more knowledgeable than most when it comes to LCD's.
What do they all have in common? First of all, the lines in the LCD are all perfectly vertical and/or horizontal. There are no signs of "bleeding" and nothing looks like a diagonal line or crack on the LCD itself. When an LCD displays these symptoms it's almost always a bad LCD but occasionally just a bad connection in the phone.
In contrast have a closer look at the LCD's that do show physical damage:
If you look closely at all of them you will note that the glass on the front shows no signs of breakage, and that all the damage was transferred into the LCD directly. The first and third one are the most obvious, but that second one is a bit more difficult to tell until you notice the diagonal crack on the LCD. You can also note there are obvious black "bleeding" areas. These ones definitely show physical damages and wouldn't be covered by any warranties.
Liquid damage is usually more obvious. Liquid damage normally shows very notable physical signs in the display with milky areas similar to this: