There's no obvious way except guessing, but there is another option now available in the latest Mastodon update.
If you're comfortable with it, you can optionally allow people to search the entire contents of your posts, which would include all of the words and phrases and not just hashtags:
https://fedi.tips/how-do-i-opt-into-or-out-of-full-text-search-on-mastodon/
(By default people are opted out of the system, for safety and privacy reasons.)