Did Southwest airlines retire flight 1380 following the accident, and with what number?
According to FlightAware, Southwest has not operated a flight with flight number 1380 since the accident flight on April 17. The flights with that number for several weeks after the accident were all been marked as cancelled in the FlightAware database; other flight numbers were used:



Southwest uses the same flight number for many flight segments in a day, but their flight schedule shows that flights from LGA to DAL leaving at around 10:30am are using the flight numbers 5227 (Sundays, 10:35) and 237 (weekdays, 10:45).