https://en.wikipedia.org/wiki/WorldTracer
"The tracking number format is AAABBNNNNN, where AAA is the airport's IATA-Code, BB is the airline's IATA-Code and NNNNN is a 5-digit tracking number. For example, the tracking number PHLDL19676 is from Philadelphia International Airport, flew on Delta Airlines, and has the tracking number of 19676."
Having looked at some examples I have, the tracking number appears to be 6 digits rather than 5 digit. If they are all numbers remove the first 4 digits which are the airline code (0257 if OS).
If your bag arrived before you why do you need to track it?