Although the heart sticker is important, no doubt, it may be that the duct tape itself is the cincher.
If this is Amy's tape, (the roll that CA took) and it is from her theatrical connections, it may be traceable to the dime! Gaffer's tape is likely quite different than your garden variety Lowe's duct tape for legal and environmental reasons. It is used in high temperature lighting conditions, movie productions, and around expensive camera and staging equipment.
If they can trace this tape to Amy and thus to Casey and the gas can, it's a win-win for the prosecution, even if the heart cannot be definitively traced.