I feel like there's a story behind this sign

Definitely, there always is

Which one ruined your weekend •_•

Well, duck.

All I wanted was a little quacktion

Probably a translate fail... i know that in spanish molestar means to molest and annoy... so they probably meant annoy :P

Fuck, fuck, fuck a duck. (No really, it's a song. Look it up.)

Though the word "molest" can be something sexual the other definition for it in the dictionary is to: "Annoy, disturb, or persecute especially with hostile intent or injurious effect." (Merriam-Webster.com) Which is probably what the maker of the sign meant. :b