We investigate the behavior of a treadmilling microswimmer in a two-dimensional unbounded domain with a semi-infinite no-slip wall. The wall can also be regarded as a probe or pipette inserted into the flow. We solve the governing evolution equations in an analytical form by utilizing complex analysis, and numerically calculate trajectories of the swimmer for several different initial positions and orientations. We then compute the probability that the treadmilling swimmers can escape the vicinity of the wall. We find that many trajectories in a ‘wedge’ around the wall are likely to escape. This suggests that inserting a probe or pipette in a suspension of organism may push away treadmilling swimmers.