The possibility readily presents itself, at least to layman like myself. I confess to being rather annoyed at situations like this, where an anomaly that looks decidedly unnatural is categorized straightaway as some freak phenomenon. It's not that scientists ought to jump to straight to ETI, and a natural explanation may well suffice, but the possibility at least ought to be broached.

See also: The prehistoric nuclear reactors in Oklo, a region in Africa. On one hand, there's a perfectly good natural explanation for them, one that predates their discovery; on the other, evidence of nuclear fission two billion years ago is a better than average candidate for evidence of alien activity, and it seems a shame that it's so obscure.

I fear that when, and if, we do find an extraterrestrial artifact, it will be casually ignored.