If packets were sent while you were disconnected, they'll be gone, but if you're disconnected for only part of the burst, duplicate ACKing will trigger retransmits.
If you were gone for the whole burst, you'll get put right by timer based retransmits.
If you're gone for long enough, most peers will timeout on unacknowledged data (although that's not in the TCP RFC), and if there's no outstanding data, most peers eventually have some sort of periodic ping and timeout (tcp keep-alives is a reasonable fallback IMHO, if your application protocol doesn't have someything, although the default of IIRC 2 hours feels long in todays world of lots of NATs and much shorter timeouts).
It may be your local gateway. Seeing no packets from your host. Attempting to refresh your MAC address via ARP. Getting no response. Generating an ICMP message as a result.
If packets were sent while you were disconnected, they'll be gone, but if you're disconnected for only part of the burst, duplicate ACKing will trigger retransmits.
If you were gone for the whole burst, you'll get put right by timer based retransmits.
If you're gone for long enough, most peers will timeout on unacknowledged data (although that's not in the TCP RFC), and if there's no outstanding data, most peers eventually have some sort of periodic ping and timeout (tcp keep-alives is a reasonable fallback IMHO, if your application protocol doesn't have someything, although the default of IIRC 2 hours feels long in todays world of lots of NATs and much shorter timeouts).