According to Icy Veins, there are 32 mage spells in standard, so your mage opponent has a 1/32 chance of discovering an Ice Block off of Babbling Book, Shimmering Tempest, Primordial Glyph, and Cabalist's Tome. But optimized decklists don't run Shimmering Tempest and almost all optimized decklists don't run Cabalist's Tome (see: Vicious Syndicate), so you're just left with Babbling Book and Primordial Ooze, assuming you're in the single-digit ranks of ladder or better.

Then you have to consider that Ice Block isn't always the best pick. In fact, it often isn't the best pick. Board clears and burn/single-target removal are usually better picks. So, in a typical game against a secret mage, your opponent will have four opportunities to grab an Ice Block with a 1/32 chance, but often the extra Ice Block is irrelevant.

In short: you're salty, suffering from confirmation bias, and not considering the context of the game. git gud