It's usually possible to recover.
webOS has not been supported for some years. You should read this article: Tip: How to Bypass Activation | pivotCE. Once you successfully boot you will almost certainly need to do this also.
You will see that it describes how to obtain the webOS doctor. This will reinstall the OS, wiping everything (including apps) except the files in the USB drive section - this is usually what you have downloaded - pictures, videos, documents, etc.
However, before you do anything, you should describe the symptoms. Is the device totally dead? Do you see anything on screen - especially when connecting the charger?
Did your friend successfully remove Android before the reset? Was it running Android only or dual booting both systems? Failure to remove Android might create issues, but I think even these can be resolved.
Does it attempt, but fail to boot? Do you for instance see a boot menu or an HP logo. Does the logo pulse? Does the LED in the 'home' button light up at all?
If you clearly describe your symtoms and if your friend can give you any information about his or her delete/reset process, then you increase the chance of getting the correct advice for your problem. It's possible that it is a minor fault and the doctor isn't necessary.
Generally, don't worry: Short of a hardware fault, It's very difficult to permanently brick a Touchpad.