"is there any way to "undo" those HSA distributions to use the tax deduction instead?"
Since these distributions were used to pay legitimate medical expenses that you needed to pay, it's implausible that these HSA distributions could be considered to be "mistaken" distributions that could be returned to the HSA. In Notice 2004-50 Q&A-37 the IRS defines a mistaken distribution as one made as a result of a "mistake of fact due to reasonable cause." Generally, a mistake of fact is one where the expense was believed to be a qualified medical expense but you later determined was not. What you describe does not seem to constitute a mistake of fact. If they were legitimately distributions made due to a mistake of fact, they would also not be expenses that could be claimed on Schedule A absent the HSA distribution.
Without returning the funds to the HSA, claiming on Schedule A a deduction related to these medical expenses would require you to treat the HSA distributions as not applied to qualified medical expenses and therefore taxable, and, if you are under age 65, to a 20% additional tax.
To avoid this situation in the future, I suggest not immediately using the HSA to pay the medical expenses, then after determining that it would not be sensible to claim the expenses on Schedule A, reimbursing yourself with a distribution from the HSA. You can reimburse yourself for qualified medical expenses at any time in the future prior to your death. This also allows for more investment growth within the HSA since the funds will remain longer in the HSA.
