Good info :)

Code Adam is an in-store procedure that quickly finds lost children. If the child is not located within 10 minutes, the police are called to assist in finding the child. Thanks to Code Adam, many children have been reunited with their loved ones.

Here's how it works. The moment you discover your child is missing, alert an employee, giving information like age, name, height, hair style, clothing, and most importantly, the shoes your child is wearing. Kidnappers are less likely to be able to change your child's shoes to disguise your child. Once that employee pages a Code Adam, all employees drop what they're doing to search for the missing child. All external doors are guarded, and every child that matches the description is approached to determine if the child is yours. If your child is found, accompanied by another adult, reasonable efforts to delay their departure are taken without putting the child, staff, or visitors at risk while law enforcement is notified of the situation including a detailed description of the adult.

Not all stores support Code Adam. Upon entering a store, check the front door/window for a blue sticker that says Code Adam (a picture of the sticker can be found at the above linked article).

Autistic meltdown vs. temper tantrum

Found this on another website and thought it was interesting. Here are some characteristics of a temper tantrum, versus an autistic meltdown:
Temper tantrum
"A temper tantrum is very straightforward. A child does not get his or her own way and, as grandma would say, "pitches a fit." This is not to discount the temper tantrum. They are not fun for anyone.
Tantrums have several qualities that distinguish them from meltdowns.
* A child having a tantrum will look occasionally to see if his or her behavior is getting a reaction.
* A child in the middle of a tantrum will take precautions to be sure they won't get hurt.
* A child who throws a tantrum will attempt to use the social situation to his or her benefit.
* When the situation is resolved, the tantrum will end as suddenly as it began.
* A tantrum will give you the feeling that the child is in control, although he would like you to think he is not.
* A tantrum is thrown to achieve a specific goal and once the goal is met, things return to normal."

Autistic meltdown
"* During a meltdown, a child with autism does not look, nor care, if those around him are reacting to his behavior.
* A child in the middle of a meltdown does not consider her own safety.
* A child in a meltdown has no interest or involvement in the social situation.
* Meltdowns will usually continue as though they are moving under their own power and wind down slowly.
* A meltdown conveys the feeling that no one is in control.
* A meltdown usually occurs because a specific want has not been permitted and after that point has been reached, nothing can satisfy the child until the situation is over."

My only disagreement with this is that I have definitely known kids with autism who would throw true temper tantrums. The intention was very definitely to manipulate. I've had other parents of kids with autism tell me the same thing- many of these kids are "capable" of using tantrums (that appear similar to meltdowns) to try and get their way.