Roku devices are provided an IP address from the DHCP server of your Router only after it has successfully connected to the network.
Basically, router broadcasts its SSID as an available network connection. The Roku device connects to this SSID and is assigned an IP address by the router. Until it connects to the network, it does not have an IP address.
When a Roku device gets "Factory Reset", it essentially returns it to a condition in which it has never been set up. (in-box from the factory). You are unfortunately going to need a replacement Roku wi-fi direct Remote to complete the setup if you have Factory Reset the Streaming Stick. (With other Roku set-top devices like an Express, Premiere, or Ultra model you can use a universal streaming remote to complete setup using the IR capabilty of the remote, but the Streaming Stick has no IR capability, thus you need a replacement Roku wi-fi direct remote.
When you weigh price of the replacement remote versus a new Roku streaming device, you may find it just as reasonable to purchase a newer device that comes with a new remote that you can use to setup both. (Basically, you now have a spare device or remote, however you look at it.)
Roku Community Streaming Expert Just another Roku user... I am not a Roku employee. Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102