Second all-grain batch, forgot OG

Just did my second all-grain batch on Friday. It went well, although I'm still learning my system. But due to getting started later than expected, it got pretty cold as we were wrapping up. It wasn't until the next morning that I realized I forgot to take an original gravity reading in our rush to get inside. I know that BeerAlchemy has a calculator that takes a hydrometer sample and a refractometer reading at the end and can tell you the estimated original gravity. I was wondering I anyone has had experience with this or has an idea of how accurate it is. Not that's it's a huge deal that I know what it started out at, but I just like to put it in my notes. But hey, either way I'll have beer. Thanks in advance.

You're right, it doesn't matter all that much assuming you got conversion. Did it taste sweet? If so, just go with what the recipe estimates, of course you won't be sure what your conversion rate is, but like you said, it should make beer.

Without that hydrometer reading you won't know what your efficiency was nor will you be able to calculate the amount of alcohol in your beer. At this point do you really care? If the beer tastes good and happens to only be 4.6% instead of 4.9% will you notice?

I've forgotten that hydrometer reading several times and it still turns out beer.