Charging a lithium ion battery below 32 degrees F damages the battery. Using the battery moderately below freezing is fine but not charging it. Make sure your battery is above 32 degrees before attempting to charge it. I assume the car is just trying to protect the battery.
Would not be the first time somebody set off a car alarm by accidentally pressing the alert button on the fob in the pocket, hence my question.The horn is only connected to the security system (and steering wheel). The beeper is used for all other alerts.
If this was the horn, not the beeper, then the security system was set off, which could be for myriad reasons.