Hotel video recorded the theft. Score believes the band was followed from a Saturday night show in Bellflower.
Score says the stolen gear included stage clothing, guitars, drums, a keyboard and hard drives containing the songs for his first solo album - 18 months of work gone.
The band used rented equipment to perform at another show Sunday and is leaving for London to continue its tour.
Flock of Seagulls is best known for its 1982 hit "I Ran (So Far Away)." Other successful singles released that same year include "Wishing (If I Had a Photograph of You)" and "Space Age Love Song":