find non-predetermined DOM insertion point?

find non-predetermined DOM insertion point?

How can jQuery locate a non-predetermined DOM insertion point?

My application relies on custom code to "bootstrap" itself. I'm wondering if similar functionality is available in jQuery?

My app works in the  following fashion:
- user places a script tag in their web page.
- my script fires and performs the following routines:
    - scriptLocation = whereAmI()? (find scripts in document, length -1)
    - insertBefore(DIV, scriptLocation);
    - use DIV as canvas, DOM target for all that follows
    - install application in DIV
Note that my custom app does not wait for any kind of "ready" state. It has no dependencies on the surrounding document. It fires inline.

My impression is that jQuery's approach ("Find something, do something") is incompatible, because it relies on a known DOM insertion point. It would seem straightforward to "query" the DOM, and find an element of known ID. That would conflict with my business constraint; I have no control over the destination page.

Are my assumptions about jQuery true? Or is there a way for a jQuery script to wake up, find its location, and the install elements there?

Apologies if this is the wrong forum. I'm a veteran OO JavaScript developer, and brand new to jQuery.