I've captured a single shot acquisition on my TDS5000 but when I try to save it+ I get an error message saying something about previewed waveforms and an empty reference - what's going on?

I've captured a single shot acquisition on my TDS5000 but when I try to save it+ I get an error message saying something about previewed waveforms and an empty reference - what's going on?

Before attempting to save, copy, or export stopped or single shot acquisitions, DO NOT CHANGE ANY CONTROL SETTINGS (i.e. Vert/Horiz scale, Vert/Horiz position, RL, Vert offset, etc). This results in changes to the acquired data and results in an error message, "Saving a previewed waveform results in an empty reference. No data will be saved to disk, copied, or exported. Please ensure the source waveform is not previewed"