You are mistaken.
And you keep using criminal acts in your examples. There is no doubt the 5th A applies to criminal activities.
Now you are saying you will have your client take the stand to testify regarding the receipt, so he IS going to testify at some point in order for the receipt to be admissible.
It isnt all of nothing. If he chooses to take the Fifth as to some questions and not to others he is participating in the proceeding and the evidence that is presented will be weighed by the trier of fact.
You are making this much more difficult than it really is.
If he testifies about buying the couch, he can not disavow the judgment against him when he loses because he took ther 5th on some questions.
I am using criminal acts in my examples because the 5th amendment is ABOUT criminal proceeding.
You said it did not apply in a civil case.
I said it sure as he** did.
If there is any possibility that an answer you give might lead to you revealing or even suggesting your involvement or knowledge of a crime, you CANNOT be forced to answer, and the exercise of that right cannot be used against you.
And if you do lose the couch, you must lose it based on the merits of the claims of the suitor.
NOT on your exercise of the fifth amendment.