When you went in September 2013, the GAC (Guest Assistance Card) was still in use. GAC had different stamps, based on what the person's needs were. There was a stamp that allowed for entry into attractions through an alternate entrance, which was probable the stamp you had.
GACs were dated and were usually dated to be valid for your length of stay (so most were 14 days or less). It could be used for every visit during the time it was valid (meaning, you did not have to get a new one each day).
Florida Residents or people with Annual Passes could get a longer date - up to 3 or even 6 months, but they did expire.
GAC was changed on October 9, 2013 to the
DAS (Disability Access Service), so if you still had a GAC last May, it would not have been valid. DAS is a much different program - it is for guests who have difficulty
waiting in the regular queue. The assistance it provides is getting a Return Time approximately equal to the current wait time so that the guest can wait outside of the line. When you return to the attraction, you use the Fastpass line.
There are no separate stamps on DAS; guests who need assistance with things like avoiding stairs or specific areas of queues ask the CM at the entrance to the attraction and the CM will assist. DAS is not needed for that, which may be why your GAC 'still worked' last May - since you didn't need anything except to explain your needs, it didn't matter that you had a GAC.
DAS cards are dated to be valid for a certain time period. Usually it is your length of stay - so in most cases less than 14 days. People with Annual Passes can get a DAS valid for a longer period - I think it is up to 60 days.
