No ashes or tephra was found in the ice sheets of Greenland or Antarctica but the supervolcano left other marks in form of very large acidity spikes (sulphates), etc:
|Source: Science Daily|
As you probably know, Toba caldera is located in Sumatra and its explosion was surely the largest supervolcano ever experienced by Humankind, leading to particularly cold period.
We know since Petraglia 2007[PPV] that peoples with an African-derived techno-culture lived in South Asia before and after the dramatic episode. However it is unclear how exactly the volcano affected our ancestors beyond that.
A. Svensson et al., Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 kyr BP). Climate of the Past, 2012. Open access ··> LINK [doi:10.5194/cpd-8-5389-2012]