Missing in 1870

It has been bugging me for awhile that there is still no good explanation for why so many Greer-Gillespie's cannot be accounted for in the 1870 U. S. federal census.

Let's start with who I do find in 1870:  John Greer, Sr., age 64, is enumerated in Bloomfield with 6 of his kids and seemingly no wife.  Those named in his household were: Mary 57; Thomas 27; George 16; Adaline 14; Flora 12; Edward 11.  It should be noted that the age & occupation for Thomas does not really match for Thomas-the-son-of-John, so maybe a different Thomas Greer is residing in the household? (Note that I did check to see if 27 was just a misread of 21, but it does not appear so.)  Also among those NOT lost in 1870 is John's oldest son, James Henry, who was enumerated in Southfield.

So the following family members cannot be accounted for:

• wife Isabella, 57 - hmmmm, it's curious, same age as Mary noted above. In 1870, daughter Mary Greer Parks was enumerated in Southfield!  So maybe Belle WAS home, although it's interesting that the name on the census is so wrong.
• John Greer, Jr. 33, 4 years before marriage to Lucy
• Charles L, 30
• Jennie, no census, but she married William Wilkins in Oakland Co. 19 Jan 1870
• Belle, 25 AND future husband J. H. Gillespie. JHG did purchase his father's land in Springfield in 1871.
• Emma, 23
• Nellie, 22 - she would marry Thomas Flinn 8 Oct 1873 in Bloomfield and then he died a couple months later
• Robert, 20 - maybe was in White Lake, MI, but that might be a different Robert
• Joseph, 18

OTHERS also missing in 1870:

• Nancy Gillespie, wife of Thomas.  She was John's aunt, sister of his mother Jane.  She would have been 90 and she died in 1872 (according to gravestone).  Where was she?
• Mary Greer Slater, 60, last seen in Bloomfield, shows up in Ludington in 1880.  It should also be noted that all 5 of her children living in 1870 are also not found on the census.

I have searched for these names in states other than Michigan, and come up empty.  I have also considered that perhaps there was a trip back to Ireland, so it is on my to-do list to look at passenger lists more carefully for this time period.  Also since there were Gillespie ties in Canada, there is some chance that some family members were there.