I'm unclear here.... Do you mean there is no way to identify manipulation. Or that there could be evidence, but none has turned up.
And would that be turned up or turned up yet, but there's still possibilities that haven't been looked at? Seems there are a lot of species and a lot of genes to consider.
The kinds of manipulation being done in laboratories would cause trouble if found in the wild. Pig genes in tomatoes and such.
The problem for ID is that everything found in the wild supports a common genetic lineage, a family tree.
The greater problem with ID is that it doesn't know how to predict anomalies, and hasn't predicted any. I suppose if we found a stray gene, someone would try to say, Ah Ha!
But predications after the fact don't carry much weight. What is it that ID would look for? None of the ID advocates have been able to come up with anything.