It's been real...
That has only happened to me once, and it was when I bypassed the lockscreen to open an email via the pull down notifications. Realized there were no softkeys when I went to back out of the gmail app.
To get them back, I just hit the power button to make it sleep... then instead of sliding to unlock when waking it, I unlocked it to the camera app. The softkeys were then present. Maybe try that if it happens again. It's only happened to me once though, so I can't say if that works every time.
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