Hey Bertie, you are not a terrible mum for not picking it up. Its not something that you can see plainly and if she has reached all her normal milestones then why would you pick it up.
As for day care, I shouldnt see why not. Just ask your carer. Is Olivia in Family Day Care or a big centre? My Olivia was in the harness but we kept her routine as normal as possible. Good luck.