It's an annoying problem in Aptana. If you make a search in files, click on a result, a file open. Then, you make another search and click in a new result file. The previous opened file is closed!
It's possible to disable this?
On the search panel there is a little inverted triangle for options (up right corner).
Click there and choose "Preferences".
Uncheck the option "Reuse editors to show matches".
That's it.