Why didn't Snape recognize the Marauder's Map?

Question

When Harry was in the corridors trying to find Peter Pettigrew at night, Snape came. Snape took that map, and had a few attempts at revealing it. When he told the map to reveal itself in the name of Professor Snape, comments from the 4 creators appeared on the map. After each comment, they put their code names: Moony (Remus Lupin), Wormtail (Peter Pettigrew), Padfoot (Sirius Black), and Prongs (James Potter).

Would Snape not have recognized those code names?

One time, when Harry was taking Occlumency lessons with Snape, he had the chance to explore Snape's thoughts in the Pensieve. In the memory, the 4 friends always talked to each other using their code names. Snape could of easily heard what they were calling each other.

If Snape did recognise the code names on the map, why did he not react? Why did he ask Lupin what this "spare bit of parchment" was?

Answer 1

The way the narration of the story goes, it seems that Prof. Snape does recognize all the code names (note that in the later books he knows who Wormtail and Padfoot are, it is safe to assume that he knew those names from his school days itself)

Since he recognized the names, he called Lupin immediately. One of his next statements to Lupin is

... Don't you think he got it directly from the manufacturers?

He is trying to imply that Lupin gave that piece of parchment to Harry that insulted Prof Snape specifically (remember that the Marauders and Snape hated each other in school)

So:
1. He recognised the code names on the map
2. He did react to being insulted by the map (he called Lupin immediately, and even accused him of possibly giving that parchment to Harry)
3. Although he knew Lupin was connected to the parchment somehow, he did not yet know what it was (Harry wiped it clean before Snape could see what was on it, and when Snape tried to view it, it only insulted him)

Answer 2

At first Snape thought it was a map of sort.

So!” said Snape, his long nostrils quivering. “Is this another treasured gift from Mr. Weasley? Or is it — something else? A letter, perhaps, written in invisible ink? Or — instructions to get into Hogsmeade without passing the dementors?”

Then, after failing to get the map to reveal itself, he assumed it must be something suspect, something that insults the questioner. At that moment, he knew exactly who made the map. Notice the first person he calls? Lupin. The insults were the same type of insults the Marauders hurled at Snape when the five of them were at school. Lupin does some quick thinking, trying to suggest Harry got the map from a joke shop

... I imagine Harry got it from a joke shop —” “Indeed?” said Snape. His jaw had gone rigid with anger. “You think a joke shop could supply him with such a thing? You don’t think it more likely that he got it directly from the manufacturers?”

That last sentence proves that Snape knows exactly where the map must have come from. He just did not know the exact purpose of the parchment, that it was the Marauder's Map.