"Have you lost your memory?"
Translation:Har du tappat minnet?
When you say a phrase in this construction relating to something on your body, you don't use a possessive adjective (min, din, sin, etc.). Instead, you make the object in the definite form. Ex: Har du ont i ryggen? -- Does your back hurt? or Skadade du benet? -- Did you hurt your leg?
We often use tappar for 'lose' when it means 'lose' as in 'accidentally drop'. For instance we have sentences like Har du tappat passet? 'Have you lost your passport?'. We also say tappa bort which is an unambiguous way of saying this.
For more abstract things though, like Han har förlorat synen 'He has lost his eyesight', you usually have to use förlora for the reason you mentioned. That's more of a rule of thumb though, you can tappa minnet and also tappa humöret 'lose your temper' and a few more. We should probably say that you can only be sure that you can use tappa if it's about things one can drop, but for others you'll have to learn for each word whether it works or not.
Also for losing games, friends etc, tappa generally doesn't fit.
Why is "... dirt minne..." incorrect?
Yes, I have read the explanations below (or above? - I never know how this is being displayed), and yes, I have read the article about body parts. My understanding is that adding a possessive pronoun might not be as common, but, at the same time, not wrong.
Have I misunderstood?