Is my PS Vita dead?

I lost my PS Vita two years ago (it ran out of battery life when I lost it), but I found it today.

However, it won't turn on. I tried to charge it for about an hour and a half now using a USB port but it still won't turn on. There isn't any indicator light or anything.

Any help would be appreciated.

The PS Vita does not turn on unless the battery is charged up to a certain minimum level. I've experienced it myself many times by letting my Vita drain completely and being unable to use it until after charging it for hours, this should be normal behavior for any PS Vita device.

On the other hand, it's weird that the Home button (aka. PS button) doesn't at least blink orange, which would indicate that it is charging. It's possible that the USB port you're using has a problem and is not charging your Vita sufficiently if at all. That's also something I experienced (once) in the past.

In my case, I was charging my PS Vita through the USB port of my Surface Book charger, but one day the Vita didn't charge at all. After opening my Surface Book, I was greeted by a message saying: "Your USB hub needs to be restarted" or something similar. Apparently, the hub "turned off" for whatever reason and stopped charging anything hooked to it (except for the Surface Book). My Surface Book managed to restart it successfully, and I haven't encountered any more problems since.

TL;DR
If you still can't turn on your Vita (10 hours at the time of writing should be more than enough), then try charging it elsewhere. Your USB hub might have encountered some problems.

The PS Vita required a lot of power to charge correctly, so using a USB port will be insufficient. I have a PS Vita, and I am unable to charge it over USB connected to my MacBook Pro, or a portable charger capable of 1A and 2.1A. It does however charge using any mains connected USB power supply.

I would recommend trying to find the official wall charger for the PS Vita and using that to charge your console. If you can't find the wall charger, see if you can find a USB port that can support 5A.