Your Squishy Liquid was all there! The Maple Administrator couldn't hand over the 30 Red Potions because your Use inventory was full, but she said 'go gather Squishy Liquid' first and only explained on the next page. That's fixed: she now tells you straight away to make room. To turn it in, free at least one Use slot (or have a Red Potion stack with space), then talk to the Maple Administrator in any town and choose Beat the Heat Project: Beginner Stage 1. It looks like you managed it right after reporting. Thanks for the report!