This past sunday here in the central valley of California it was 106 degrees. While traveling down the freeway I lost the lead wheel weight off the rear wheel. I can't tell the difference in the ride, I only noticed it missing when I was cleaning my bike after the ride. How important is it that I should get it into the shop for replacement.

 

I wouldn't worry about it if you don't notice a difference. You'll be changing the rear tire soon enough. Have it rebalanced then.

 

Do you remember how much weight was added to balance the wheel? I assume that half of the tape is still on the wheel. Just clean it off and reapply new weights. Or guess based on the length of tape remaining. That should be closer then no weight at all.

This should be a warranty item, but since you are questioning the merits of balancing I guess that you do not want to take the time off from riding.