By Elena Fabrichnaya MOSCOW (Reuters) – Around a dozen aggrieved retail investors met with the senior management of Russia’s SPB Exchange this week, demanding the recovery of their foreign currency assets blocked by U.S. sanctions. Russia’s second-largest stock exchange, which specialises in trading foreign shares, last week said Washington’s restrictions were blocking more than two thirds of clients’ foreign currency funds and the rest would be transferred to them in roubles. “We have lost access in full to our foreign securities that were purchased through SPB Exchange and denominated in U.S…