There is an option on the iPad to delete photos from the original host device as photos are copied across. The deletion process actually only deletes the first character of the file name. So long as nothing has been written to the card since, various programs can restore the file names and hopefully allow some if not all of the images to be recovered.
Immediately copy all the images to another device for storage once you have used the recovery software.
For future reference, don't ever let memory cards be used in someone elses device without first operating the write protect switch on the memory card unless you are completely happy with them writing or deleting information on your card. Even a simple copy process can write data regarding the last time the file was accessed and corrupt the card when you go to try and use it in your own device again.
If possible use a wireless transfer method such as wifi or bluetooth to copy images between devices.
Never trust anyone with the original and only copy of a file!