Not necessarily. In the aforementioned context, I feel it would be particularly confusing.
Thong style bikinis are increasingly popular these days. You would wear both those and thong sandals to a beach, so if you work in a beach shop and someone asks if you have thongs, it may not be clear. Thong as a term for sandal has also really fallen out of use these days. I still run into people who have no clue a thong could mean a sandal, so I don't really find it surprising at all. It may be a generational thing, though, now that I think of it. My grandma would call them thong sandals, but most of the people I know who've gotten totally confused over the term have been younger than me and have never heard the term in relation to a shoe.