I've discovered bald patches 1 month 3 weeks after my hair transplant, have my grafts been damaged?

It is normal to lose transplanted hairs weeks after surgery.  It may take 6 to 12 months to see new hairs grow out.

Without an in-person consultation, its hard to diagnose what’s causing the bald patches. If the bald spots are occurring in the recipient transplant zone, its possible they are cycling through the hair growth cycle (which involves shedding). Remember that its only been 2 months since your surgery. We don’t usually see the desired results until 6 months – 1 year post-op. Gentle massaging of the scalp like during washing done after 2 weeks post-op would not generally cause damage to the grafts.
If the bald patches are occurring in your native hair areas, you may be experiencing shock loss. Shock loss is a pretty common after effect of hair transplant surgery. If these hairs were healthy and strong they will most likely grow back during the next hair growth cycle. If they were weak and part of your hair loss progression, they may not grow back. This is why its important to utilize multiple methods to fight hair loss. Hair transplants don’t stop the progression of continued hair loss. Rogaine can help maintain the native hair you have, while preventing future hair loss and works great for hair transplant patients. You should meet with a qualified and experienced hair transplant surgeon who specializes in the medical management of hair loss to discuss all of your options. 

If you are referring to the actual recipient area grafts, many of these shed so that they may look bald. If you are talking about your native hair, then you might have developed shock loss (see below)