I know this is a little while after the original post, but I stumbled across this the other night looking for the same answer, as I had dropped my Blackjack and then realized that the speaker wasn't working.
After seeing the phrase "and if that doesn't work, then you got screwed...", I said to myself "Oh HECK NO!" and decided to fix it myself.
If you still have the phone, I'm sure it's not under warranty any more. If that's the case (as was with me), here we go.
I removed the sim card and battery and took the phone apart. This is done by taking the 6 Phillips head screws out of the back.
When that's done, you can see how the speaker is attached to the back of the phone, but some wires with a square black connector are attached to the speaker. If that's not connected to the motherboard of the phone, there's your problem.
On the right side of the motherboard of the phone, there's a little black/silver square "seat" that looks suspiciously like the connector from the speaker. That connector on the speaker connects to the "seat" by snapping into place. It looks a little tricky to do because the wires aren't really long enough to snap the connector into place unless the back of the phone is almost completely on the phone.
What I did to snap it back in was put the back on the phone and leave a little space to guide the connector and push it back in with the screwdriver. I then screwed the back on and put the sim card and battery back in. It was THAT simple.