As Michel Grand pointed out, a number of people have folded a model almost identical to Pocket Heart before me. You can use any of the instructions listed below, with the difference being that in step two where these designers decided to just fold the model in half through both layers, in Pocket Heart I create two symmetric reverse folds on the left and the right (but following the same crease lines as them). This creates the pocket inside the heart and aligns the paper layers more symmetrically.
- Heart Card by Jeremy Shafer (1996)
- Srdce by Ondrej Cibulka (2013) (click through to the first page after the cover here)
- Cœur en 6 plis by Stephane Gigandet (2015)
- Broken Hearts by Emily Monaghan published in BOS Magazine #290 (02-2015), page 34