I've checked and it appears that Gramblr support the History option which means that you have the possibility to check all the images you've uploaded. Use the button on the left side of the application that says History to check all the images. You should also check the profile where you uploaded the images, because it's possible Instagram deleted them. They don't actually support the Gramblr application and forbid using 3rd party apps to upload images on their service.
For any other issues, get in touch with the developers through their contact form: http://gramblr.com/uploader/#contact