What Jeshi said is correct, it's unlikely that you could be made to forget something of that nature just because making someone "forget" through hypnosis is more along the lines of not bothering to remember or forgetting to care about connecting specific dots. If you start filling in some of those dots though, the brain will pick up and fill in the rest.
Ever notice how some B movies will reuse special effects from a completely different movie? Or
(more often in the past than now) a studio will make two entirely different but slightly similar movies with the same actors, sets, props, and costumes with different scripts? Catch part of the reused bit or see the set+actors+props and sit there scratching your head wondering why it doesn't line up with what you remember?
It would probably take far far more work than it would be worth, but you could obfuscate things enough to make it difficult to pick up the right trail of dots among all the other winding piles of dots. It still wouldn't be the first time though, finding out the significance to
"would you kindly" would only work the first time for example... and again... it would probably be way more work than it would be worth.