I don't understand what is happening

Thicc boy musta been datin doctor daddy (nd helpin him look for yuchen?) Nd yucken found out doctor daddy was lyin abt his "disappearance"...my guess..

Yuchen did disappear, at least from Luoyi's perspective. It's just that Luoyi didn't go out of province as Yuchen thought he did. That was the whole reason Yuchen went abroad as his mother had originally asked him to, because he thought Luoyi had been lying about wanting to watch him draw.