B-I-N Primer Gallon / Scam and abuse!

I went through the check out line with 4 gallons of BIN Primer. There was a $5 rebate for each gallon purchased, or so they adverted. The young clerk put red tape on four of the gallons but only rang up one. I didn't notice until he got done and gave me the total. I realized what had happened and told him, you are giving me 3 gallons for free. The manager was very grateful and thanked me for my honesty. I do it for me but am happy to pass on the practice to young people and all others. Here is the problem: I sent in all four of my receipts with proper paperwork and got only one rebate for $5 back from Menards. I asked how to fix this next time I went in and was told to contact the rebate service. I never got my other $15 of merchandise credit checks. Sad, isn't it.