Hi Karin.
I'll leave the whereabouts of the post to others. Possibly the Writing Process area would have been my bet.
With regards to your use of "us", I've (mis)used English in similar terms myself (one that springs to mind was "You Only Love You" when technically it should be "You Only Love Yourself" - but it fit the beat this way). There's no hard and fast rule I feel. 'We haven't seen "us" in a while' can sound okay, especially when it fits the rhythm.
Take solace in Shakespeare. When he wrote his plays he didn't give a damn about what was acceptable English or not. He changed it to suit his needs. Enough people seemed to understand what he was saying and there are about 1700 words now used in the English language that he invented to back that argument up.
If you're still unsure, post up your lyrics here and we can take a look with you.