Based on what you are describing, I doubt it was temperature related. From the manual:
Operating Temperature Range -10°C to +50°C (+14°F to +122°F)
Storage Temperature Range -20°C to +50°C (-4°F to +122°F)
Charging Temperature Range 0°C to +40°C (+32°F to +104°F)
What I have heard reported is direct sunlight affecting the LCD screen (screen goes all black). Getting it out of the direct sun, allowing it to cool down, even pouring some water on it allows it to recover fairly quickly. I would imagine the same for other electronic components pushed up against their thermal limits would recover once you powered down and then got the machine ambient temperature back into the normal range. Those effects are typically immediate and also recover quickly. A factory reset should really not be needed for a transient thermal problem (it can't hurt, but I don't really see it helping). If you actually did some real permanent thermal damage to the electronics or the battery, doing a factory reset would not fix the problem either. So it does sound like the machine powered up in some mode and was noisy perhaps due to a previous user setting adjustment that was innocuous where the detector was previously being used but not so good at the new site due to some local EMI, I suspect. The factory reset just got you back to default settings and you were good. You didn't say whether you tried doing a noise cancel before you ran sensitivity down. Anyway, I don't think you did any thermal damage to electronics and based on what you described even though a car can heat up significantly higher than the air temp even with the windows cracked, doubt having it sit in the car caused what you were seeing. Most important to keep it out of direct sunlight.
Regarding the temp ranges above, be sure to obey the charging temperature range limits. Charging the battery cold or hot (charging temperature range) can cause permanent damage to the battery despite it's thermal shutdown circuits. Charging during cold ambient temperatures is especially not recommended for lithium ion batteries. HTH.