Eh, well, I don't think it matters much either way. When I was applying for residency, I listed an observership I'd had as a med student, but I deleted it for this round of applications. If it was meaningful and/or HO-relevant, I think it would be totally reasonable to include it. Basically, don't worry too much. It's not going to be the thing that makes-or-breaks your application, IMHO.
To be honest, I think that PDs expect these kinds of things. It happens to applicants every single year. I don't think this is worth worrying about either. Nothing you can do about it anyway, haha. Best of luck to you this cycle!