Well, you haven't lost anything. It's always good to have a spare set of crystals on a different channel, just in case someone else is on your frequency. That way you can swap them out and still run with him.
The next step would be to try a new receiver on the frequency of your radio. If a friend has the same setup, you can put your crystal in his Rx and see if the servos move.
Again, the LHS can help you check your setup to determine what you'll need.
If you KNOW that all your contacts, wires and switches are fine, and it wasn't the crystal, the receiver is next in line.
There's no need to buy a new receiver unless it solves the problem. If that's not it, the transmitter is next, but it's kind of unlikely.
Also, if you know someone with the same transmitter, then match the crystal to the one in your truck and test it. That way you'll know the problem is the Radio.
By the way, what kind of truck is this, and what is the brand of the Radio and Rx?