Putting the truck on a stand and blipping the throttle might not catch it. With the tires free spinning, there's little to no load on the motor.

Explain in more details what happens when you loose connectivity. Does it just come back on it's own? After how long?

Don't know if you'd have enough time to get to the truck when it happened again, but if possible drive it around without the body and when the problem occurs set your radio on the ground and run and look at the receiver and see if it's got a solid LED.

Is the problem happening immediately after a hard acceleration?

Not sure what 2.4ghz system the Duratrax radio uses, but you might want to try and rebind the receiver. I had glitching problems on a DSSS radio that was solved by rebinding.