Photoelectron angular distributions (PADs) resulting from 800 and 1300 nm strong-field ionization of impulsively aligned $mathrmCF_3mathrmI$ molecules were analyzed using time-dependent density functional theory (TDDFT). The normalized difference between the PADs for aligned and antialigned molecules displays large modulations in the high-energy recollision plateau that are assigned to the diffraction of backscattered photoelectrons. The TDDFT calculations reveal that, in spite of their 2.6 eV energy difference, ionization from the HOMO-1 orbital contributes to the diffraction pattern on the same footing as ionization from the doubly degenerate HOMO orbital.