Packet loss of any medium.

If a protocol has a mechanism of tracking lost packets you can determine them if a filter exists. TCP has one for example: tcp.analysis.retransmission will show all packets Wireshark determined (or believes) to be retransmissions. Or you could look for tcp.analysis.lost_segment, which will show all packets that have one or more missing previous packets. Both filters have drawbacks though, because missing packets (and "retransmissions") are not always really missing - they often are just out of order arrivals. So you would have to confirm each occurrence manually, which is a ton of work in a large trace file.

If you're looking at protocols that do not track lost packets as part of the protocol you're basically down to the "needle in the haystack" problem, because you'll have to verify each communication by hand. And often enough you can't even tell if something was lost or is just arriving late.