During a 5 hour trip to Phoenix with an outside temp of 100 degrees, the Hybrid warning came on and dropped us out os CC (85mph).
All of the hybrid interactions ceased on the display but car operated "normally" with only the IC system working.
Once we stopped at the next place for food and fuel, and restarted the car, normal hybrid operation returned however the hybrid warning remained.
It had also previously thrown a P0401 (insufficient EGR flow) error that was uncorrected but the EGR error did not seem consequential enough to cancel this trip and I can't say whether the EGR issue contributed to the hybrid error.

We had the codes read and inspected at a local hybrid battery replacement shop and although they do not work on RX450h models, they read the codes, and checked the pump flow at the hybrid coolant reservoir since the one of the possible things the P2601 indicates is a low coolant flow.

Since we have an extended warranty we decided not to reset the codes at the time but decided after looking through all of the warranty info to just reset the codes and see if they came back.
I bought my own ELM327 V2.1 Alerón Brand. OBD2 Bluetooth Scanner on Amazon and the pro version of Car Scanner for iOS for less than $20 and read and reset the codes.
I was fully expecting the EGR code to come back and planned to pull and clean the carbon from the EGR valve but for whatever reason neither code has returned in several weeks.
Maybe a few hard accelerations cleaned it out but it is likely it will have to be cleaned at some point.

The hybrid warning may have just been a fluke or I also read that a temperature differential in the fluid may cause the error too so it may have been a confluence of factors that cause the error but so far so good.

Hope someone finds this helpful or comment if you'd like.