I am rather curious what the guy really had to ask.... May be he just wanted a beer!
A suspect looking total stranger approaching you in a parking lot wanting to "ask you something", especially at 11:30pm, should look somewhere else if they "just want a beer".
Parking lots are common hunting grounds for criminals and since most criminals choose their victims largely based on the would be victim's response to the "interview" ("Hey man, do you have the time/can I use your cell phone/do you have change for a 20/etc/etc), it is best to not take part in any potential interview.
Therefore, being curious about what the guy wants is curiosity that is best disposed of; especially with one's pregnant wife at your side.
If our "thirsty" stranger needed assistance, well he could have just gone into the store and asked for assistance.
As far as I'm concerned, a stranger approaching you in the parking lot is a scam or even a potential mugging until proven otherwise...and I am not interested in playing along to prove that its not.