Yes, it's a green checkmark in VV:O! Different games have different color, and I'm working on VF2 right now, which has orange checkmarks. (I've edited my post, too, after checking it).

The game is designed to automatically restore both the food doubler and the tech doubler, since they are non-consumable purchases. Since the game seems to "know" that you've already purchased them, look for some sparkles in the center of the research table and the food bin. I've attached a screen shot of how they look on the research table for you to compare with.

If there are no indications (other than the game telling you that you already have them), it would be very helpful to know which app store you use for your purchases and whether you have been continuously using the same user account at that store, how you started the game over (using the Start Over option on the menu, clearing the app data from settings, uninstall/reinstall) and whether or not you have installed the game on any new devices since purchasing the doublers. Also, when you first went to the upgrades screen, did you see a brief message stating that purchases had been restored? It's sometimes really, really fleeting, but it's a green message box with white text in it.

I am as interested in understanding what the problem is as you are!