The more appropriate phrase would be "if by any chance someone does".
Notice the wording in the phrase "If someone should do", where the word "do" is in present tense. It suggests a hypothetical situation or scenario where such an action occur. Therefore, a phrase synonymous to that would be a phrase that is expressed in the present tense as well.
It is important to realize that the phrase "if by any chance someone did" is in the past tense and presents a slight difference. In this context, it suggests a hypothetical situation or scenario where such an action has occurred. Despite this, it does not present any differences in meaning from the first phrase. Both phrases are suggesting the same hypothetical scenario with one in present tense, and one in past tense.
Although both phrases are grammatically correct and can be used as substitutes for the phrase "If someone should do", the former phrase is more suitable.

The more appropriate phrase would be "if by any chance someone does".

Notice the wording in the phrase "If someone should do", where the word "do" is in present tense. It suggests a hypothetical situation or scenario where such an action occur. Therefore, a phrase synonymous to that would be a phrase that is expressed in the present tense as well.

It is important to realize that the phrase "if by any chance someone did" is in the past tense and presents a slight difference. In this context, it suggests a hypothetical situation or scenario where such an action has occurred. Despite this, it does not present any differences in meaning from the first phrase. Both phrases are suggesting the same hypothetical scenario with one in present tense, and one in past tense.

Although both phrases are grammatically correct and can be used as substitutes for the phrase "If someone should do", the former phrase is more suitable.

The more appropriate phrase would be "if by any chance someone does".
Notice the wording in the phrase "If someone should do", where the word "do" is in present tense. It suggests a hypothetical situation or scenario where such an action occur. Therefore, a phrase synonymous to that would be a phrase that is expressed in the present tense as well.
It is important to realize that the phrase "if by any chance someone did" is in the past tense and presents a slight difference. In this context, it suggests a hypothetical situation or scenario where such an action has occurred. Despite this, it does not present any differences in meaning from the first phrase. Both phrases are suggesting the same hypothetical scenario with one in present tense, and one in past tense. Although both phrases are grammatically correct and can be used as substitutes for the phrase "If someone should do", the former phrase is more suitable.

The more appropriate phrase would be "if by any chance someone does".
Notice the wording in the phrase "If someone should do", where the word "do" is in present tense. It suggests a hypothetical situation or scenario where such an action occur. Therefore, a phrase synonymous to that would be a phrase that is expressed in the present tense as well.
It is important to realize that the phrase "if by any chance someone did" is in the past tense and presents a slight difference. In this context, it suggests a hypothetical situation or scenario where such an action has occurred. Despite this, it does not present any differences in meaning from the first phrase. Both phrases are suggesting the same hypothetical scenario with one in present tense, and one in past tense. 
Although both phrases are grammatically correct and can be used as substitutes for the phrase "If someone should do", the former phrase is more suitable.