I put my anorak on and discovered from ACARS records for D-AIHA that it looks like this happened on 7th March when 'HA operated LH 440 FRA- IAH.
The next records for HA indicate the aircraft was ferried from JFK to Frankfurt overnight 11/12 March, so presumeably went IAH -JFK also on 11th (as it was reported still at IAH on 11th earlier on this thread). It has not been noted on ACARS since arriving at FRA on 12th.
Suzeman