.mat file missing data after restarting Matlab

I saved a Matlab variable as a .mat file, then reopened, giving it a new name. This new variable appeared to be complete; however, if I restart Matlab and open the same .mat file, some (but not all) of the data is missing. What could be causing this?

[Jeffrey Clark]

@Gareth,

1. If you are saving variables of user defined class(es) the same classes have to be available when loading the .mat file - the path during load may not include where the classes are.
2. If you are saving variables containing handles (either graphics or from classes using the handle superclass) special save and load procedures may be needed.

Foreither of the above you should look at Object Save and Load and Handle Classes - MATLAB & Simulink (mathworks.com)