In 31:33-34 We find Lavan coming to look for his stolen idols. He comes to Yaakov's convoy and makes his accusations. Yaakov denies everything and allows Lavan to conduct a search (even with no search warrant).
The passuk describes how Lavan looked inside the tents of Yaakov, Leah and the two maidservants and found no trace of his stolen idols. Lavan then went to Rachel's tent and, the passuk says, Rachel hid them in the camelsack upon which she sat and Lavan conducted a thorough search feeling around the whole tent and did not find them.
By the previous searches it simply says "He went to their tents and did not find them". By Rachel's tent it says, "He went and searched and felt around.."
It seems from the wording that he conducted a much more thorough search in Rachel's tent than he did in the other tents.
Lavan knew who had taken his idols. He knew it was Rachel and not any of the others. He knew because he knew them, he knew Rachel and he knew who was capable of this.
If I get home from work and find an electronic item (for example) taken apart and broken, sure I will ask each kid if he is the one who did it. But in truth I already know which one it was because I know there is only one capable of doing it and I know which one that is.
Lavan looked in the other tents because he had to, because he could not come out and accuse Rachel with no proof. he had to make a cursory search in the other tents, but he did not want to waste too much time and energy because he "knew" they were not there anyway.
So when Lavan searched the other tents, he did what he had to do. But when he got to Rachel's tent he really knew it would be somewhere there, so he conducted a much more thorough search.