Et tu, Brute?

Question: Can Instant Investigator be used in scientific pursuits, such as quickly analyzing an archaeological site?

Alas, no. Instant Investigator is specifically designed to discover details pertinent to foul play, shenanigans and criminal activity; unless your archaeological site happens to be the forum in which Caesar was murdered, Instant Investigator will not help you learn any more details about it than you could through other methods. And even then, the knack probably isn't going to help you much; the difficulty is equal to the number of days that have passed since the event in question, so unless you can get 751,000 or so on your Wits + Investigation rolls, you're not going to be able to quickly reconstruct the exact scene of Caesar's death any more accurately than anything else that happened centuries ago.

For most situations, eyeballing a scene to try to get an idea of what happened there recently is a good old garden-variety Wits + Investigation roll; it's not as detailed as Instant Investigator unless you really knock the roll out of the park, but it gets you as much immediate, quick-on-the-uptake information on any given situation as your Wits allows. Most scientific investigations will probably be Perception or Intelligence + Investigation rolls instead, sacrificing the quick overview in favor of spending some time to get more in-depth details.