I've deleted Google Play Store. How can I reinstall it? I've been having an issue with my apps where an error "Package file is invalid" keeps appearing. I read a tutorial somewhere which told me to "uninstall updates" for the Google Play Store application. I was told doing this would uninstall the application, and then the device would automatically reinstall Google Play Store.

I did this, restarted my phone, but the application never reappeared.

I think tried downloading an .apk file to install this manually, but on install the application wouldn't load.

Has anyone done this before? How can I reinstall this application? I believe I need it for all future downloads and updates to my applications.

For the record, my phone is not rooted.
You cannot uninstall the PlayStore/GoogleMarket app without having your device rooted -- so as Shedo guessed, you probably just uninstalled the latest update. Which means, the original app included with your firmware takes over -- and probably is called "Market" (the original name of the Playstore, before some market specialists started toying with the name).

So look out for an icon with a green bag, labeled "Market", that's it. Go ahead and start it, browse a bit, leave it. The Play Store App should be forced back on your device automatically -- maybe not immediately, but it usually doesn't take long.