Will you be returning to your home before going to the facility for your drug test? If so you could put it in a cooler to keep it cold until you get home. Then microwave it for 15-30 seconds until its about 100 degrees F. Then you can crotch it and your body will maintain it at a 90-100 degree F temperature. If you're also worried you can use those hot hands people use in their gloves in the winter time. You can buy them at Wal-mart in the camping section for under a dollar.

To summarize if it was me:

1.) I would try to put it in a cooler immediately.

2.) Return home and microwave it to the appropriate temperature.

3.) Put it into a 3 oz shampoo bottle (you can buy empty ones at Wal-Greens for cheap).

4.) Crotch it and use a hot hands until you are in the facility parking lot. Then remove the hot hands before entering the facility.

5.) Drink plenty of water so you have a good long void so you can mask the noise of you pouring the clean sample into the cup. Also don't forget to pour a little into the toilet to give the toilet bowl some color.

6.) Finally, measure the temperature to make sure it's correct. Also, try to find a digital thermometer that doesn't beep. I found one on Amazon. The brand is called Kaz and it was around 5$.

That's my opinion though, I hope it works out for you.