For Bell, the first thing you need to do is examine the spot where she normally is, until then you don't know she's missing. Yeah, she's no longer there, but you need to check there first, another cowgirl will mention she's wandered off somewhere. Then, she should be in one of three places: Jail in New Ark (going to assume Arlene was involved somehow), Transylvania, or the Forest Park. Might need to sleep a day to give Bell time to get wherever she is.
For the Lil Shop of Horrors, it's more placeholder than anything right now, but you need the "living underwear" from Marin before Dalvie will let you in.
Hope this helps!