Recordings shouldn't just disappear. A number of 360 boxes received an over the air update earlier this week and since then some forum members have indicated they have also lost recordings, so this may apply to yourself.
You haven't indicated whether or not you turned your box off for the period you were away, however it's advisable to leave it turned on or in standby overnight, so it can download and install any system updates and EPG changes.
Losing recording though is usually due to a failing hard drive. Perform a factory reset via Settings > System > Factory Reset. You are given 2 options
Keep Recordings and Format Disk
Choose Keep Recordings, which means you won't lose your recordings, and any planned recordings, or series links you've set up. You may have to sign into your apps such as iPlayer, Prime, Netflix and ITVX again. Also Match frame rate and Standby power consumption may go back to their default settings if you have changed them.
Another indicator of hard drive issues is if you having problems following pausing a live program and then playing it back. Another indicator of hard drive problems is having to keep signing into apps like iPlayer (this can also happen if you disconnect everything over night). I find that I have to sign into most apps if I turn the 360 off either overnight, or reboot it during the day.