The bars usually have the weight stamped/molded right into them. Probably hard to see those marks now that you melted the bars.
Good mixture you mentioned. For .38spl (bullets at ~800fps or so), etc. I don't even bother with the solder mix. Shoot straight wheel weights. Zip for leading problem.
Most bars I've had are ~2lbs. If they're (were) about 16-18" long, you probably had the 2lbers & can add another 27lbs of WW.
In any event, you're not dead in the water. Cast & shoot what you have & be a bit more careful next time.