luckily, i found my membership card. I _______ for it all afternoon
which one is correct? I had looked for it all afternoon or I had been looking for it all afternoon.
Either is correct though neither is necessary.
I found my card. I looked for it all afternoon.
Obviously, searching preceded discovery.
Using a perfect tense makes the sequence explicit, but that sequence is so clearly implied by meaning that it is not necessary. Nevertheless, in writing or formal speech, it is advisable to use a perfect tense in such situations because writing and formal speech do not get the assistance of tone of voice, opportunity for questions, etc. that conversation receives.
The same kind of linguistic logic applies here to the difference between past perfect and past perfect continuous. The words “all afternoon” make clear that the search was not completed in almost an instant. There is no necessity for using a continuous tense to make clear that the search was annoyingly protracted. A good writer may elect to use a continuous tense in such a situation because it emphasizes the duration of the search, but I doubt one native speaker in a thousand would do so in normal conversation.
The scenario is complicated by the fact that many native speakers will exclaim "I found my wallet!" when what they mean is "At last, I have found my wallet, just now.". Moreover, "all afternoon" could be today or some day well in the past.
So, if the contextually intended meaning of "found" in the statement is "found just now", the speaker wouldn't use the past perfect to describe their search but would use the present perfect: I have been looking for it all afternoon.
But if the contextually intended meaning of "found" in their statement is not "just now" and the speaker is relaying a story about a search conducted well in the past, then they would be more likely to use the past perfect: When I was on the ferry last summer I lost my wallet but luckily I found it under a chair. I had been looking for it all afternoon and was (or had become) quite frazzled.