In the first sentence, have lost is not past tense, but a present perfect construction. The same goes for 've lost in the second sentence. The third verb phrase, could be catching . . . up, is made up of the modal verb could followed by the plain form of be and the -ing form of catch up.
The present perfect construction is used, among other things, to describe a present state that results from a past action. In this case, although the phones were lost at some indeterminate time in the past, the discussion is about the situation at the time of speaking. The construction could be catching . . . up is a modal progressive form and describes a continuing action. It contrasts with could catch . . . up, which describes a single action.
There is no need to rephrase either sentence. In formal writing, there would be a period rather than a comma between months and at, but this appears to be a spoken rather than a written dialogue.