The Sitelist.xml file packaged with the agent installer (Framepkg.exe) is what decides which SPIPE site (epo server or agent handler) is contacted.
If ePO is listed as the preferred site, then agent will first attempt to connect to it and on success, get an updated sitelist that contains a list of agent handlers based on the agent handler assignment rules.
Ofcourse this wont work if there is no network path to ePo server. So a way out would be to update the Sitelist.xml file by copying it from a machine that is set to report to the Agent handler in question.
You can update an existing agent with updated sitelist.xml by using this command:
frminst.exe /install=agent /siteinfo=c:\sitelist.xml
For this to work, you willl also have to copy the srpubkey.bin and reqseckey.bin files from the master repository to the same folder where you put the updated sitelist.xml (in this e.g. c:\)