If the 360 has deleted your recordings and planned recordings it's a sign that the box is faulty, especially if it does it more than once. You can either call Virgin on 150 from a Virgin phone, mobile or landline, or 0345 454 1111 from any other phone to report a fault, or wait here for one of the forum team to pick this up which might be 2 to 3 day's.
You could also try a factory reset of the 360, and if you haven't got any recordings you might as well go for the format disk option and if or 'when' the box deletes everything again then phone Virgin.
They might suggest you set the Auto delete option to off, it probably already is and shouldn't affect planned recordings but you can check by doing the following;
Press Home > Recordings > Recorded > View All > Manage Storage > Enter your pin > Auto delete when space needed > Set to Off.
You can also do a quick check of the hard drive by pausing and rewinding live TV if that doesn't work then the box definitely needs replacing.