The original authors (Janecka et al., J. Med. Chem., 1994, 37, 2238-41) used a slightly less aggressive mobile phase than we did, but we did not get much movement of the compound under their conditions IIRC. It was 94:5:1 CHCl3/MeOH/HOAc. I just reread this section, and they also used: n-BuOH:py:AcOH:H2O in the ratio 30:10:3:12, and they saw a higher Rf in this system than in the chloroform-containing system.
Between you and me, one can never rule out that an undergraduate student made a mistake in how the solvent was prepared, but it is difficult to be certain that this was the problem (they might have used the wrong acid, for example). I was thinking of using roughly 25% methanol in a couple of portions to pull it away from the silica once we unpack the column. However there will be dissolved silica at this point. If we remove the solvent, I would predict that some silica will come out with it. Maybe we can ignore this silica. although it will add to our mass.