Consider an example where host-A is sending data to host-B. While the fragments traverses many routers in between, some of the fragments are lost. So now the router identifies this and waits for that lost packet to arrive or it just routes it to the next router? If this is true, how does the lost packet be recovered?
There's no mechanism to request a fragment be resent. The entire packet cannot be reassembled, so the entire packet will have to be resent. This is why Fragmentation Is Bad(tm).
Routers typically do not care about fragmentation. They pass things on exactly as they receive them. (unless it's the source of the fragmentation.) As such, the router will be unaware of missing fragments.
(I'm ignoring the practice of "virtual reassembly".)