With respect to ideas, if you have established some kind of agreement in advance (a boundary) so that possession by the new person(s) does not entail a transfer of ownership (as is similarly the case with a rental property), then the relationship of ownership of the idea by the original person might be propertly considered to continue. 

If no agreement (boundary) is created, then the idea, once communicated to the other person, ceases to be a property of the first person.

It isn't always necessary to establish boundaries in space, if you can accurately establish them in time (the fourth dimension). 

All contracts and agreements exist in a time sequence, whether they are necessarily bounded in space (length, width, and height) or not.

Time is the essential ingredient in virtually all agreements, including most credit arrangements.

For example, one man agrees to work in the employ of another man for a week.

The boundary of this agreement relates in a primary way to the period of time of one week.  The employer agrees to pay a certain amount of money after the week is past; the employee agrees to accept that amount of money in exchange for so many hours/days/weeks/etc of work.