If they were old-style paint/ink marked ICs, your agressive solvent mixture has probably totally stripped the markings.
Assuming modern ICs, you've probably scrubbed the brown burnt epoxy residue out of the microscopic pits left by the laser marking, so reducing the contrast till the markings are virtually invisible. If so, try applying a dot from a light coloured or metallic paint marker and smearing it over the top of the IC with your fingertip, then wiping off the excess with cartridge paper moistened with WD40. Done with care, some paint residue will remain in the microscopic pits and improve the contrast.