In "The Scavenger Vortex," Penny wears a purple-pink shirt. In the car scenes, her shirt appears light pink and purple. This is because for car scenes, a blue or lime-green screen is used to create the moving car effect. The blue or lime-green color is chosen because no one's skin color is blue or lime-green, therefore their faces won't be affected. Although Penny could have changed her shirt, it appears the same purple-pink as it did in at the beginning.
When Howard sings into the rock, he clasps it in both hands. When he turns so Amy can join him, he is suddenly only holding it in his left hand.
After choosing teams, Sheldon asks Penny if she knows what the odds are of picking her name out the hat. After she says "No", he replies "It's not hard, one in five." However that is the probability of choosing her name out of the hat, not the odds. Odds are the probability of an event occurring relative to them not occurring. In this case the odds would have been 1/4 or 0.25.
In the geology lab, Sheldon tells Penny that silicon is the most common element in the earth's crust. This is incorrect - silicon is the 2nd most common element in the earth's crust, the most common being oxygen.
Stage lights are visible in the bowling ball Sheldon holds.
Rasj states that he 'slipped' the coins they eventually find in each of their pockets earlier that day. It is very implausible that none of them would check their pockets throughout the entire day.
In the title and within the episode, the game is referred to as a scavenger hunt. A scavenger hunt is where participants look for a list of items. The game they are playing in this episode is called a treasure hunt, where the participants use clues to find out where the next clue is hidden and eventually arrive at the treasure, in this case a gold coin.
Sheldon says that "He" is the abbreviation for Helium. As a physicist with a PhD, he would know that "He" is the symbol, not the abbreviation, for Helium.