The first thing I would do is pull the dipstick and see if you have any oil on the stick.
The place that did the oil may of forgot to put oil in.
How long has it been since your last oil change? Isuzu are know to burn through oil, possible reasons are listed in my FAQ.
Have there been others with this happening? Yup, I've read at least 25 posts like yours, and they are all due to a spun bearing due to low oil.
I hate to say this but if you didn't purchase an extended warranty you're out of luck.
You can purchase a used engine at:
www.car-parts.com
good luck!
-Ryan