Are some of my photos missing because I removed them from the Picasa application?

Picasa does not "contain" your pictures. Your photos are in folders on your hard disk and Picasa monitors/edits them in those folders. Therefore, as you found out, if you delete a photo from Picasa, it is also deleted from your hard disk. The deleted photos -should- be in your Recycle Bin. Since they aren't, you'll have to do 1 of two things. Either reload them from the camera that took them, or use a "deleted file recovery" utility program to scan your disk and look for the photos and restore them. I have included a link to a free utility below that is said to be pretty good. Others are available - use Google to search for them.

Now - to enable more of your photos to be found, try not to save/write anything to the hard disk until you get the pictures back. The reason is that writing a new file may over-lay the area where the deleted picture exists.

Good Luck.

yeah, they may be deleted. try file recovery tool to get them back. A popular one is Asoftech Recovery. This tool can deep scan the memory card and recover your lost files back without requiring extra skills. Here is the steps might be helpful to you:

1. Connect the memory card to computer. Under "My Computer", note the drive letter assigned to your camera's memory card (usually G: or H:).

2. Download this program on your compute. here is the link: http://www.asoftech.com/apr/

3. Install and start the program. then click on settings on top right part of the program, check all and click OK.

4. select the drive where your lost files located, click Start. Now the scanning process will start to search the deleted files. After a while you will then get a list of recoverable files.

5. Press Recover to perform full recovery.