Honesty is the best Policy!?

Last Sunday I treat my son a dinner at one of the fast food here in Ormoc. I ordered a chicken meal worth 60php plus a glass of ice tea for me that costs 18php so all in all the total was 78php so i gave 200php to the waiter and then he gave it to the cashier then returned with the number. so i thought they will give me the change as soon as they deliver our food.....After 15 or 20 minutes the waiter deliver our orders, my son eat his food and i drank my ice tea without remembering the change and after eating we proceed to watch the basketball championship games of the two gigantic teams here in the city.the game lasted for almost 2 hours and after watching we went home and that's the time that i remembered....... so the next day, i went to the place, i told the cashier about my change and she can still recall my orders, the total price and the money i paid. she told me that the change was given to the waiter who delivered our orders and she said to wait for him in the afternoon and he should pay me the exact amount........at 4pm i went again and there i talked to the waiter and he seems very bothered and he cant even talked to me in the eye and at an instant their manager approaches me and talked to me and eventually blamed me for the mistake and that they cannot anymore produce the 122php change because it was already given to other customers..........?????? i was really angry and frustrated but i did not freaked out because i am just testing their honesty. i just turned - around and said its okey because i don't want to argue with this people who are so dishonest.
Well , i admit that i do have a fault here but as human being and as a mother who went on giving birth and was given some medical treatment sometimes have overlook certain things and that's normal.
Because of the incident, i swear not to eat anymore there even if they offer cheap prices and delicious foods.