Your pack will probably be OK. Since the voltage was low but not totally flat, and for a short time, I'd recommend charging it at the 0.1C rate as you thought. Do it in a safe place and monitor it but do it soon. The longer the battery stays below the minimum of 3V per cell the greater the risk of permanent damage due to chemical reaction. You may find that it has lost some capacity but only testing will tell.

Also, since it is a 3s pack you need to check for cell imbalance between cells in series. Such a low discharge can cause the cells in series to discharge to different voltages. If your pack is assembled as a single shrink-wrapped unit then the only way to test for this will be to remove the shrink wrap so you can get to the individual cell connections to test the voltage with a volt meter. If the cells are imbalanced you will need to charge each group of paralleled cells separately to a maximum of 4.2V per paralleled set.