Hmmm
I can't find any other option that sets the default in the Find box. There is a "FindRecord" method and action (macros) that has a "Match" parameter - if you set this to "acAnywhere" with the "OnlyCurrentField" parameter set to "acCurrent", this will give you what you want. However this would require that you create your own custom search form that is launched when you press Ctrl-F, and that you customise the menu bar to replace the Edit/Find option.
There would be a bit of work involved - do you feel lucky?
[VBA]
DoCmd.FindRecord Me.txtSearch, acAnywhere, False, , True, acCurrent
[/VBA]