Streaming tokens using Superfluid requires you to lock a certain amount of buffer or deposit which is taken out of your balance.
The parameter for this buffer is currently 4 hours' worth of the streamed asset on mainnets, and only 1 hour on testnets.
This is an incentive mechanism to ensure users cancel their Superfluid streams, to prevent the output stream from ever surpassing the sender's Super Token balance.
You will see this warning when you stream for the first time, and if your stream is for a short duration.
If you allow your stream to run out of funds, you will lose the buffer. It is your responsibility to cancel your stream manually before this occurs. The dashboard features warnings to alert you of low balances on your streams.
Unfortunately, there is no way of recovering lost funds if you ignore these warnings.