How is knocking on someone's door an "incursion" or a "surprise attack"?
That the attack depended on surprise and intimidation doesn't invalidate the use of attack or raid imho, that's the preferred outcome of any police raid too (and websters definition of attack is "to set upon or work against forcefully", no mention of physical violence).
A PI who's even vaguely trying to obey the law DEFINITELY does not expressly threaten you with violence, and won't allow any more than the barest implication either.
If the PI brings a bunch of big goons with guns and they imply that they'll kill you if you don't turn the thing over, then sure, that's a raid. But also you'd presumably call 911 immediately and file a police report stating that you were robbed.