What method of insertion are you using to "save" the drawings? Insert File, Insert Picture, Insert PDF...
What options did you specify when you inserted them?
Have you selected the new "optimize for interactive content" data formatting option for this field?
Are you using Drag and Drop? In fileMaker 11 on windows systems, drag and drop did an insert object-which used OLE technology to find and open the original when double clicked. OLE is not supported in FileMaker 12 so you can no longer use insert object or get that result with drag and drop. Drag and drop now works identically on both mac and windows. It inserts a copy of the file. This is the same as using Insert File without selecting "store a reference" when doing so.
In both fileMaker 11 and 12, if you use Insert File and select the "store a reference" option, you should be able to open the file by double clicking the container field. This does not work with Insert Picture or Insert PDF. It does not work if "store a reference" is not selected. If the "interactive" option is selected for a container field, it cannot open the file via double click either.
Export Field Contents can be used to open the file no matter how it was inserted, but this creates a new copy of your file at whatever location your export Field Contents action specifies. If you make changes in this file, the changes are saved back to this new copy, not the copy stored/referenced in the container field. To preserve those changes, you'd then have to re-insert the modified copy of your file into the container field.