I accidentally left my bottle of Latisse in my suitcase in a hot car for 5-7 hours. Did I ruin its effectiveness?

All studies to date would suggest the Latisse is fine. A 2011 study by Johnson and colleagues looked at how the concentration of Latisse (and other prostaglandins) changed when exposed to elevated temperatures including 37 C and 50 C for 3, 6,9, 15 or 30 days. Interestingly there was no change in the concentration of Latisse over time. Of course if your Latisse reached even higher temperatures, we enter a grey area and don't fully know the answer. However Latisse can withstand quite a bit of heat due to its remarkable thermable stability.



Reference 
Thermal stability of bimatoprost, latanoprost, and travoprost under simulated daily use.
Johnson TV, et al. J Ocul Pharmacol Ther. 2011.

The studies support that latisse should be fine even when exposed to hot temperatures as in a parked car.