What's interesting is that when I check my posts in my profile, they only go back about 10 months. If I click on hash tags that I create in some of those posts, I can find posts that go back almost two years. Now, if look for those hash tags in the search function, I frequently get no return. I think this is a limitation in the client. Functionally there is a difference between tapping a hash tag and searching a hash tag. This is likely a dev issue in my client.