Also, if you use a lds, most keep boat records. We keep a record of every boat trip, with diver information. We keep them for years. I have had people come to me and ask to go through them so they could reconstruct logbooks. It is documentation that you were on those dives. We even keep general times for first in, last out, surface intervals.... On our spreadsheet are water temps, tides.... If your lds is well organized, you should be able to get them back. If htey were out of town trips, your credit card will have dates and amounts so you can reconstruct from there.
At the end of the day, you don't want the absolute minimum dives required, so missing a few shouldn't be a huge deal. Two words. Dive computer. Easy and downloadable. You are set. And print out a spreadsheet every few months so you have a hard copy. Good Luck.