Oops... did I burn up my Arduino??

Alright guys I feel like an idiot but here's what happened... I built a project on my Arduino, which was hooked to my laptop for power and communication. Everything was fine, no problems, and I finished my project (actually a pretty cool one involving a pressure sensor with some customizeable settings, but that's beside the point.)

After I finished my project, I went over to a friend's house and wanted to show him what I had built. I did not have my laptop on me at that point and he gets weird about me using his computer for stuff (even usb power) so I used usb wall charger for a cell phone and plugged my usb to type-B connector into it, and powered my Arduino with that. I should have checked first of course, but I assumed tha

My assumption here was that the voltage from this source would be 5 volts, because that is the standard voltage for usb devices. I did not measure the usb-B output voltage, but I can only assume that it would also be 5 volts because the type of connector should not affect the output voltage. The current should have been regulated by any internal resistance in my Arduino and therefore I did not think this would negatively impact my device.

Here's the problem... I showed my friend my project and it worked fine, no issues. I unplugged it and set it aside for the time being. That was yesterday, and today I went to plug in my project and the Arduino does not power up. By this, I mean that the power LED does not light up, and there is no indication of any activity in the circuit. I tried connecting the Arduino to my PC and also via a 9v battery to the barrel jack, and no power anywhere.

So my question is, did I kill my poor Arduino?? I am an electrical engineering student and so murdering a component here and there is not a big deal, but of course I love my Arduino and hope I did not kill him, and would rather not drop the $20-$40 to buy a new unit.

If anyone has any help/suggestions, I am all ears!! Thank you

As the Arduino runs on 5 volts, you may have fried the 5 volt regulator. The one next to the barrel connector.
If you have a multimeter you can check that with power connected.

From what you stated, I don't see how you burnt anything. But, when you power it, is there anything plugged into the arduino? If yes, disconnect everything then power it. If lights don't come on, probe around with a DMM and see where you are losing voltage.

Thank you both for your replies. As it turns out, I did NOT fry my Arduino, what happened is there is a SP6T switch that was grounding out the 5v pin on the Arduino, causing it to short and therefore not power up. I found the problem and now my Arduino is back to 100%!

Guess I wasn't wrong after all, haha.