My advice, start keeping a detailed spreadsheet NOW. I wish I had done this from the beginning. We've had so many moves that there's a good chance a lot of our records are misplaced, or faded, or or aged enough that the bank can't help us with the records anymore.
Make a Google Docs (or your prefered cloud storage method) file where you keep scans of your qualified medical expenses, label these by date, payee, and amount for easy searching.
In that same folder, make a Google spreadsheet where you have a little more information, like method of payment and whether or not it has been redeemed from the HSA. Keep the spreadsheet updated every time you move funds around.
If you're ever in a tight spot and really need money, you can reimburse yourself from the HSA. In thirty years when you're retired, you can pull out funds selectively as needed and still reap the tax advantages. If the IRS raises an eyebrow, you got it covered.