The only time I've seen Leandro Lo swept in the past couple years of footage available on youtube, is from a player who sits up to a single leg, or hooks Leandro's lead leg with a kouchi or kosoto type reaping action like in Judo. Kouchi is a reaping actin in between the legs, kosoto would be a reaping action hooking from outside the legs. Otavio, below, uses a kosoto action.
If you're too lazy to look all that up, Otavio Sousa does it at 1:24 of this match:
I posted about it here, and highlighted Otavio Sousa pulling off a rare sweep against Leandro Lo at the Copa Podio. Turns out Gilbert Durinho found similar success and almost got to the back in this match at about 2:25. You'll notice Durinho sweeps/hooks from in between the legs: