Bacon & Eggs - S5-E2
Corrected entry: Season 5, Episode "Bacon and Eggs." After multiple rejections, Grace finally decides to call Leo. She pulls his business card out of her wallet, presumably to look up his number, but barely glances at the card as she dials. (This would be plausible if she memorized his number, but if so, why pull the card out?)
Correction: She was looking through all the cards to see if there was anyone worth dating. when she saw his card she pulled to ponder whether to date him, not to find his number.