If the coolant was low, it went somewhere. It does not evaporate.
Pull the speed sensor on the drive unit ASAP. if it has moisture on it, the drive unit has an internal leak and the drive unit's inverter is about to be scrap. Discontinue powering it on until repaired, or you'll be "rebuilding" the DU with inverter boards from some other donor DU.
Or, just budget for DU replacement.
2014 Rav4 EV, Shoreline Blue Pearl, #2609, first use 04Jun2014, 49k miles (Aug2017), OpenEV-SE 40A. First DU replacement May2018 59k.
2018 Model 3 LR AWD, blue. 9.6kw solar