The short answer would be no. COI is a single maternally inherited marker, so it may provide relevant information on the directionality of introgression, or give you an idea about the geographic origin or the number of independent hybridisation events (in relation to the parental species' diversity). But identying hybrids themselves critically depends on nuclear genetic markers (and then COI can provide the additionally useful information stated above). Morphology may or may not be a good advisor in any case. Hope this helps.

Further to @Christoph Sandrock's answer: If your species are clearly different morphologically, finding the "wrong" CO1 in one of them would be an indicator of hybridisation, unless your assumptions about the morphological uniqueness

Dear Christoph Sandrock

Thank you very much for such a detailed answer.