Help with Consolidation and Subjugation mission of the berber campaign

Not sure if this is a bug or if I lost it but when one of Tariq's soldiers gives the announcement that a treb is available, I simply can't find it on the map. I resign and view the map, no treb. I thought it was garrisoned somewhere, nope. I lost my initial two after I blundered an attack on a wonder. The setting is on Hard.