Image files in Bluetooth folder not showing up in Gallery



I am using Samsung Galaxy Y. The images that are in my Bluetooth folder of the SD card are not showing up in gallery. They do show up when the files are received. But once the phone is restarted, they are no longer shown in Gallery. The images can be viewed by going to the Bluetooth folder in My Files. Also, they are again visible when moved to other folders, like Images folder. What is the problem and how can I rectify it? Please help.
Thanks in advance.