Legal Question in Criminal Law in Louisiana

It depends. While you did not steal the card itself (it is not stealing to take something that was thrown away), you may be committing theft by fraud by using the card, depending on the circumstances.

If these points are not transferable and you fraudulently held yourself out to be the cardholder then you did commit theft by fraud. You cannot pretend to be someone else to obtain benefits to which you are not entitled.

If these points are fully transferrable and can be used by anyone (sort of like a bearer bond or cash), then it is not any sort of theft. It is perfectly legal.

Now, all of this assumes as true your statement that the card was (and was intended to be) discarded, not lost or simply dropped, misplaced, etc. In order to qualify as having been discarded, it would have to be thrown into the trash by the person who owned it. If someone just drops somehting, they don't give up their rights to it.