HSG vs Saline Sonogram

Hi all. When we first went to our fertility clinic last year they did a HSG prior to me doing IUIs (HSG came out fine but IUIs didn’t work). Fast forward to this year. We did IVF and have a couple of embryos, and are planning a transfer. Clinic now has me do a Saline Sonogram prior to transfer, and they found a polyp that they will remove first via hysteroscopy prior to transfer cycle. I’m just wondering ... if I had this polyp all along wouldn’t that that lowered my IUI success rate too? I’m wondering why they didn’t test me for this last year!! What’s everyone’s experience? When did you have a HSG vs. Saline Sonogram ... before IUI, IVF, or just as a general new infertility patient? I’m so frustrated thinking this is something they could have caught earlier!