I just had my pads, rotor and drum replaced on my 2009 Honda Fit by a highly rated garage. Two things I noticed while driving home. When completely stopped, the brake pedal slowly lowers to basically full deflection (this was not the case before). Also, the brake light on the dashboard is lit up.

I'm no car maintenance expert, but I have some guesses. Is the brake fluid low? Is there a brake fluid leak? Bottom line is, should I bring it back tomorrow? I paid a lot of money and I feel like something is wrong.

 

I would check the brake fluid first thing(low fluid level can cause the light to come on), avoid driving the car and contact the garage ASAP

If the reservoir still is full of fluid it might be a failed master cylinder but im not sure

air in the lines also will cause a spongy pedal but Im not sure how bad it would be for it to go all the way to the floor

Sounds like they really messed it up , I hope they wil fix their mistakes without hassling you

 

Pedal drops slowly, and fluid missing....LEAK.
Did they replace a caliper? Did they flush brake fluid? What did they do that would cause a leak?
I'm guessing a line, fitting, or bleeder they touched is not tight and leaking.

Take it back to the shop ASAP.
Maybe ask if they would prefer to tow it in for you (on THEIR dime) so you don't crash it due to loss of brakes. A judge would love to hear about the crash, I'm sure.