How did my Xcode project get changed from iOS project to an OSX project?

I've been doing only iOS development and never made an OSX app. In the iOS project I'm working on now I see that suddenly Xcode thinks it's an OSX project. The all my framework files are shown in red (missing), and lots of the options in the project panel show choices that are only appropriate for OSX such as "deployment target", which offers only 10.4, 10.5, 10.6 etc. and in Build Settings the Valid Architecture shows i386 x86_64 with no drop-down options.

What happened? How can I change this back to an iOS project?

could be 2 late to answer this question, however, this answer might help someone in the future, as the above answer wasn't helpful for me, so here is what I have done.

1- on the left top corner of Xcode click on the scheme.

2- click edit scheme

3- in the new window change "Executable" from non to the name of your project scheme "target"

4- on the top where it says "My Mac 64-bit" if it didn't changed automatically to iPhone/iPad change it manually.

5- if there wasn't any option, in bottom of the window click "Manage Schemes" and make sure the check box next to your project scheme is checked.

hope this could help and save anyone time.