How do you know it was offline? By this I mean how were you monitoring it? If via remote which remote was it? If local radio what was the location of the radio? Did you try a second source to confirm it was off air?
Many people make the mistake of monitoring via a remote and when they do not hear the station they assume it is offline. Most often the remote is offline or the audio is lagged out. If you are not directly monitoring a station, if you are using a remote, particularly one without a visual indication of signal (such as a waterfall), and an anticipated signal is NOT present, you should always confirm with a second source. If you are directly monitoring, using a local radio, then a remote can often confirm if the station is missing due to lack of signal or if it is really just conditions.
Unless you can confirm the reason for lack of signal an offline UVB (or any signal) does not mean it is actually offline, it might just mean whatever you are using to receive is not hearing it.
UVB-76 is reported off line many, many times a year. Almost all such reports are incorrect, and in reality only the source the listener was using was off line or not working correctly. Of course, this station does go off air from time to time, probably once a month or so on average.
T!