I think I've worked out the missing lines:

A married man will bring you shame,
For he'll go home tomorrow.
I'd rather spend my nights alone
Strummin' my guitaro, strummin' my guitaro.
I've been in love a dozen times.
I'll love again tomorrow,
But now my weary heart and mind
Must hide with my guitaro, hide with my guitaro.

A single man will take your heart
And in its place leave sorrow.
Though someone else can have my part,
I'll caress my guitaro, caress my guitaro.
I've been married. I've been single.
They both led to sorrow.
But I’ll admit the night was cold
Strummin' my guitaro, strummin' my guitaro, strummin' my guitaro.