where could have this appeared from??

[hendy_5450]

where could this line have appeared from

[Eugene Tyson]

Could be underline - as it's encompassing the tab

Could be a Paragraph Rule - Above/Below

Could be Paragraph Shading

Could be Paragraph Broder

Could be as Strikesthrough
Could be a floating frame

Could be an anchored frame

Need more info, even a sample file.

[Mike Witherell]

When you select it; does it light up a Character Style?