The abbreviation rule of a measure word
“昨天晚上买了（一）张彩票，结果中奖了。”，it indicates you buy One ticket. You'd better use 几张 to indicate that you bought several tickets. I am not saying you are wrong by 买了些彩票, but in practice, 些 is often used to describe uncountable nouns. For example, 我买了一些水果。这些事情。说些什么？

you can say '昨天晚上买了彩票', which conveys the fact/behavior itself you bought some/a lottery ticket(s) (how many you bought is not the point/important; Or you deliberately don't want to tell how many you bought; Or people don't care the number of tickets you bought.)