Assuming that your feet were still in the hammock & got wet anyway, that you have an orientation problem*. If (for example) you is hanging N - S & the wind is coming from the South (or even SE or SW) you got wet feet OR head depending on how you lay. When I had a smaller tarp I would hang as close to across the wind as possible & if not fully possible to do so, I would hang my hammock as close to the lee end of the tarp thereby allowing a bit of space to keep my feet (or head) dry.
As suggested, a larger tarp reduces that problem, & I got a HUGE tarp, so I don't get wet, almost regardless of orientation. Plus I can close either or both ends if need be. But my tarp ain't for everyone, so,,,,,
*You would have had issues anyway with a wet hammock. A rained on hammock usually means wet insulation.