Life Time Warranty - Yet the onus is on me to prove my purchase, why?

I purchased front and rear shock absorbers that were sold under the promotion banner that stated "Life time warranty". I was never informed of any additional "fine print" or that I should retain the receipt for this purpose, I understand that one usually does but in this insident I unfortunately no longer have it. Now approximately 5 years later I am told that the partcular Supa Quick branch changed their computer system and that my vehicle particulars captured at the time are no longer available. I am now unable to claim my "Life time warranty"!