Did you have HDHP coverage on July 1 of the current tax year? If so, you are considered to have HDHP coverage for the entire month, even if you stopped it later in the month.
Thus, your $1,500 contribution in July would be considered valid, so long as you did not exceed the annual HSA contribution limit for your situation (your annual limit will be reduced based on the number of months you had HDHP coverage and no conflicting coverage like Medicare).
Note that even if you lose the ability to contribute to the HSA, you can still continue to make distributions from the HSA (i.e., spend money on qualified medical expenses). You can do this until the HSA is exhausted.
There is nothing to claim as a loss, because you haven't lost anything. Just continue to use the HSA until the funds are exhausted.
[Edited 3/17/2020 3:36 pm CDT - updated answer]
