Sorry for the novel, but looking for any advice from anyone who's dealt with bedbugs in the vicinity.

Situation is we live in a brownstone on the third floor and keep our strollers and bunting in the lobby of our building (on the second floor). Yesterday morning I was putting the bunting over our umbrella stroller and found what I got an exterminator to confirm was an immature bed bug (UGH UGH) on the bunting. The bunting itself is a month old and literally has only been to 3 places: our daycare a handful of times, to the park where we leave it in the stroller, and to a local coffee shop where we also leave it in the stroller. No signs of bed bugs at our daycare (that we know of, but who knows) and zero signs of bedbugs in our actual apartment. I am super crazy clean and no one in the building (4 apartments total) has seen any sign of them, no one has gotten a single bite. The landlord who lives below us has had a bunch of workers in the lobby and her place, on the same floor, in the past week doing painting and other work, I'm wondering if it possibly came from that, but of course no one wants to be patient zero in this situation.
Anyway. I got my landlord to take this seriously and she called her exterminator on the spot, he's coming tomorrow to go WW3 on the lobby and hallways, and I'm having him preventatively spray our apartment, too. I'm going to wash and dry all the linens and the stroller fabrics, and he's going to treat the stroller frames with alcohol.

Has anyone here had a similar situation? REALLY appreciate any advice anyone can offer.