It sounds a little strange – was Moshe feeling his pockets, searching his drawers, looking in case he had misplaced the money? Moshe Rabeinu, the person who epitomized “da’as,” could not recall what he had done?
The Kotzker (quoted in the She’eiris Menachem here) explained that Moshe’s accounting was not like something done by the IRS or like a corporate annual report – it was a spiritual accounting. After the Mishkan was completed, Moshe was able to look back and see how the madreiga of ruchniyus of each item in the Mishkan corresponded exactly to the level of kavanah invested by the person who donated for it. The donations of Ploni who had tremendous kavanos l’shem shamayim may have been used for the aron or in the kodesh kodashim; the donations of a different Ploni, whose kavanos were a little less intense, may have been used in an outer wall. You got exactly what you spiritually paid for, so to speak.
Moshe was left with was 1775 shekalim that he identified as has having been tossed in without the right kavanos, without the real l’shem shamayim that a Mishkan demanded. Moshe couldn’t figure out how these monies translated into a davar sheb’kedusha. How did they have a place in the Mishkan?
G-d revealed the answer: They were the hooks that stood atop the poles. There are people who are amudim: They are like the poles that keep the building upright, they have all the right kavanos and the l’shem shamayim. But even those who fall short of those ideals still have a place: They just need to “hook-up” with one of those amudim and attach to their presence. Recognizing one's own shortcomings and making up for them by following someone greater is itself a tremendous accomplishment.
The gemara has a din that something that a mechubar la’tahor is itself tahor, something attached to taharah is itself treated as tahor. Reading a deeper meaning into this halacha, the Yehudi haKadosh was asked how it makes sense: Someone who is tahor has worked day and night to achieve a certain spiritual level; why should someone who just attaches himself to that individual deserve the same benefit?
The answer: It’s harder to be a true mechubar than it is to be a tahor.
It’s an age old problem -- everyone wants to be an Indian chief, but no one wants to be an Indian. Hiskashrus to someone bigger, hisbatlus to someone bigger, pushing one's ego into the back seat, is a very hard thing to do, and what’s worse is that no one sees you doing it and gives you credit. Even Moshe Rabeinu almost missed it. We need to celebrate not just the amudim, but the vavim l'amudim as well.