Is the apartment in a larger building or more like a duplex arrangement? If its a complex or tower, the bugs might not have even come from your unit in the first place. In My last apartment, the landlords had to exterminate my section because people in a unit on the other side of the building had a severe roach problem. So while the building was u shaped and the infestation was on the opposite arm from my apartment, they still had to bomb the whole frigging building or the bugs would just come back.